You get to pick and choose where to set the grammar goalposts? The only difference here is that you have preconceived notions of what a psion 'should be' and I don't. That class could easily function solely on psychic powers, it would just be focused in a way that doesn't match up with your expectations, but if it functions based on psionic powers it is indeed a psion, whether or not you like it. I don't think you get to gatekeep the definition of psion quite that closely. If they wrote it up as, say, a fantasy Jedi it would still be a psion then too. Your definition isn't the same as the definition.It's exactly the same. A class is the class. Other than in 1e were Psionics were a tack on, they have been a pure casting class. What a Psion is has been well established, and it's a pure casting class.
What you describe is NOT a Psion "sho nuff." Rather, it's a class with psionics, "sho nuff." That's it.