First, as Chris said, check out the work done at that company. “Motion Graphics” is a term that covers lots of ground – LOTS – and it may or may not be the case that your knowledge overlaps with what they need.
The work you display on your Website is highly original and creative, but if I had to assess your knoweledge of AE based on this work I would guess you have stayed away from some pretty mainstream elements. It’s not clear that you are comfortable with 3D movement, cameras, lights, text effects, particles, strokes, … all of which may be a must – or again, they may be irrelevant to the type of work your prospective employer is doing.
Take a look, for instance, at the samples over at the (world famous!) ayato (https://www.ayatoweb.com/ae_tips_e.html). This is certainly motion graphics, it’s all AE (with the obvious Photoshop/Illustrator thrown in), and it’s like completely orthogonal to your work. Take a look at his final renders and ask yourself if you would know how to do this in AE from scratch… if you can, you’re an AE master. If you don’t even know where to begin, you may be missing some “particular things you should know about After Effects as a motion graphics designer”. Again, Ayato’s work is top notch and you shouldn’t feel bad if you can’t do it right of the bat, but take a look at the step-by-step descriptions and ask yourself if you’re familiar with those elements of AE.
Don’t get me wrong, I’m not saying that this broadcast-type motion graphics are better or more sophisticated than your work. They’re just different. If you’re asking about what a motion graphics designer should know in AE, this may be part of it.
Hope that helps,
AA