Crop factor has nothing to do with T-stop. T-stop is strictly about light transmission which affects exposure. If a lens could be 100% transmissive the T-stop and f-number of the lens would be the same number, but they would still be measures of different things. T-stop measures how much light is passed through the lens, f-stop measures the size of the aperture compared to the focal length of the lens. The f-number of a lens is what determines depth of field. With regards to exposure, crop factor has nothing to do with f-stop either.

The only way a 50mm f/2 lens "acts" like a 100mm f/4 lens on a µ4/3 camera is with regard to angle of view and depth of field when the camera position is the same for the FF camera with 50mm f/2 lens and the µ4/3 camera with the same 50mm f/2 lens. With regard to exposure, the 50mm f/2 lens is still an f/2 lens.

When you use a 10mm T2.1 lens on a µ4/3 camera it will still be a 10mm T2.1 lens. You'll get an angle of view similar to a 20mm lens on a 35mm/FF camera. You'll get DoF similar to an f/4.2 lens on a 35mm/FF camera, but you'll still get the exposure of a 10mm T2.1 lens - because that's the lens you are using.

T-stops and f-stops are measures of how much light per unit area is allowed through the lens. When you use a smaller sensor, the same amount of light per unit area is falling on the sensor. But since the sensor is smaller, it is just collecting less total light.

If you have a one acre field and I have a two acre field and it rains uniformly on both our fields we'll both get 1/2 inch of rain, but I'll have received twice as much total water because I have twice as much surface upon which the same amount of rain per square foot fell.

For more, please see:
How to achieve full-frame look/view on a crop-sensor - without changing the lens?
Why do DPReview's charts show the G7X II as having an aperture around f/8?
Can a smaller sensor's "crop factor" be used to calculate the exact increase in depth of field?