Another poorly-designed question. A better survey question would be: Have you found this to be true for YOU?

I can't say if it's true for some. I can only say it's not true for me. I do have a hard time seeing how it could be true for anyone, unless you are being forced to use piano as your only composition platform. As one tool among many it could only INCREASE your idea-generation opportunities, it seems to me. But I also know there are people out there who don't think like me.

I will say that, because of my limitations on piano, the ideas I generate on piano often have certain characteristics (e.g. it's great for exploring line cliches, moving one note while the rest of the chord stays the same, stuff like that). But 1) Those are cool types of ideas! and 2) It is only ONE of the composition tools I use.

Sometimes I noodle on piano, sometimes I noodle on guitar. Sometimes a lyric line will come to me complete with a rough idea of melody and I will flesh out from there. Sometimes I just get an idea of things I want to try and I experiment within a scoring program like MuseScore. Or all of that in combination and iteration.

In my view, adding tools to your repertoire will only stifle you if you let them. (And, BTW, often deliberately constraining yourself is a great wat to be creative! It can certainly be an interesting exercise.)