ETTR is advocated so that you expose enough until you don't clip highlights

That would be wrong without adding the word "important" or something similar, like in "don't clip important highlights".

so that you can get less signal to noise ratio in the shadows

Not less, but better (actually, higher; as noise is lower).

ETTL is advocated because the shadows preserve better details than highlights

I think "ETTL" is not mentioned in the article at all. The term ETTL becomes outright redundant if we agree important highlights, not just any highlights, should not be clipped.

There is no ETTR or ETTL per se. There is technically optimized exposure, and creative exposure (a whole different story). There is exposure for the scene, and exposure for the main subject in the scene. The following is mostly about the "noise and resolution optimized" approach to "exposure for the scene" for relatively wide dynamic range scenes which we want to capture as accurate and as full as possible in a single exposure.

"Expose to the right" rule is in fact exposing for the shadows without blowing out important highlights (that is, preserving those highlights, like in ETTL :) ) where one needs to preserve a hint of texture; or, in other words, give the shot as much light as possible (through aperture control and shutter speed, mostly; as ISO setting is not a part of the exposure, raising it does not add light, and it is raised when opening the aperture wider and setting slower shutter speed is not an option anymore) without damaging the important highlights. What are those important highlights depends on the scene and is determined by the photographer.

To determine what are those highlights I can afford to blow out I ask myself a question - will the photo be ruined if I let go this or that texture? Next, can I frame closer, or crop, to exclude the areas that will be blown out because the dynamic range of the scene as I framed it is wider than what my camera is capable of reproducing? Or maybe I need to change my position with respect to Sun, or shoot under different light, or to use some fill light (flash, reflectors, etc.), or shoot at a different time; or to use a polarizing or gradient filter, or some combination of the above.

To determine the dynamic range of the scene I use spotmeter to meter from the important highlights and important shadows and see what is the difference between those 2 measurements. If it is more than 8 stops I start to decide if I want to shoot the scene as it is: there is a good chance that shadows will be of lower quality, with more noise, less resolution, and more colour skews than I want them. Yes, some would say modern cameras are capable of much more than 8 stops; but the spotmeter (even my hand-held 2-degree Sekonic) integrate over a certain area, and the in-camera ones are prone to flare on top of that. So, from experimentation I decided that 8 stops is a good number, and will never go for more than 10 stops in a single exposure even with the best current cameras and prime lenses.

It is worth mentioning that histogram, and especially in-camera histogram, is not the best way to determine the proper exposure for the scene that includes light sources and specular highlights because it does not show where the blown-out highlights are in the scene. Most of the cases those specular highlights and light sources need to be let go. Histogram in this case indicates overexposure, but in fact it is not the case. "Blinkies" show the locations of the blown-out highlights, highlighting what areas are clipped in the scene.

If you are shooting raw, one of the important things is to know how much headroom there is between the metered exposure and clipping point in raw. This number varies between camera models and makes, and even ISO settings, from 2.5 stops (equivalent to 18% grey) to 4 stops - and even more for "fake ISO" settings (that is, when the raw data is to be multiplied during the raw conversion). Searching for "exposure meter calibration" should result in several useful hits.

If the scene is 8 stops according to spotmeter or less, it can be exposed based on the measurements from shadow area that needs to be rendered in detail; with exposure compensation that depends on the calibration of your camera (something about -4EV). This allows for close to least possible noise. Same strategy if the scene measures wider but the highlights are not important. If the highlights are important, the measurement is taken from the highlights where you want to preserve some details and texture and about +3 EV is added.

Otherwise, the old school advice still stands. The exposure is based on the most important midtones (something like measure the forehead of the model or the back side of your own hand and add +1 EV; or measuring incident light and adjusting, taking into account camera calibration). Those midtones need to be exposed as high as possible, once again, without clipping important shadows and important highlights. This way the most important midtones will have the best definition, resolution, acutance, colour fidelity, least noise, and will need least editing while postprocessing the image.