There is overlap between the two terms, as you'll see as you browse the lists of both at LensHero. Basically, they're two different directions from which to approach the problem of narrowing down lens choice, and the site offers both approaches.

A wide angle lens has a specific definition without much flexibility — it's any lens with a wide field of view, generally considered to start at around a focal length of 35mm on a traditional 35mm film camera. So that's pretty straightforward: if the lens matches that, it should be in the list.

On the other hand, any lens can be a landscape lens — even a narrow focal length telephoto lens. A landscape photograph is simply one which portrays natural scenery of an area, and a wide angle lens is the easiest way to capture a vista, but not the only one.

So, from that point of view, the landscape lens list could be every lens ever, but there are some characteristics which are useful to landscape photography which may not be present in all wide angle lenses. That helps narrow down the list in a useful way. And, there are features which a lens might have which are of no real relevance to most landscape photography, so lenses which make those a design priority are generally off the list as well.

One aspect of this is good performance stopped-down for maximum depth of field. Most lenses fit this, but a lens for landscapes may offer even-more-constricted-than-normal choices — many lenses designed for APS-C DSLRs don't close down past f/16 because of the diffraction limit, but for landscapes, you may prioritize depth of field over overall sharpness.

The flipside of this aspect is that good wide-open performance isn't very important, and for that matter, the "speed" of a lens doesn't matter — if you're going to be shooting at f/11 or f/16 or beyond, it doesn't make a difference whether the lens is able to open to f/1.4 or f/2.8. Providing good image quality at these fast apertures requires heavy and expensive lens elements, so a lens designed with landscape photography in mind instead can be cheaper, smaller, and lighter with no disadvantage.

Another aspect is across-the-frame sharpness. If you're taking pictures of centered subjects, it's usually acceptable (or for portraits, maybe even desirable) for the corners of the frame to be softer. For a landscape, this can be problematic, particularly if you have noticeable foreground objects near the corner of the frame (a frequent choice, as a nearby tree or rock often makes for a nice composition).

Back to the LensHero site... I notice that for Pentax mount, the DA 14mm f/2.8 tops the list for wide angle, but the DA 15mm f/4 Limited gets that honor for landscape. This makes perfect sense given the characteristics above: the 15mm Limited isn't as fast, but when stopped down, it's sharper across the frame. And as a bonus, the 15mm is much smaller and lighter, which is a definite advantage if you're taking your landscape photograph from a mountaintop.