The term you're looking for is "creative constraint". Some people (I am one of them) need the constraint enforced more brutally in order for it to work at all.
Sure, I could develop a minimalistic game using the Unity engine – but I find it much easier when I'm using the Pico-8 fantasy console to force myself to do so.
Similarly, I could cook a varied vegetable meal any day of the week – but I find it much easier when I'm using vegetarianism to force myself to do so.
I have casually wondered what term to use to describe this phenomenon myself, and now I have it.
It’s why I like pixel art, chiptunes, polaroids, one-pot stews and modern video games for retro consoles among many other things. Sometimes I feel like this is why so many great artists come from restrictive religious backgrounds as well.
Sure, I could develop a minimalistic game using the Unity engine – but I find it much easier when I'm using the Pico-8 fantasy console to force myself to do so.
Similarly, I could cook a varied vegetable meal any day of the week – but I find it much easier when I'm using vegetarianism to force myself to do so.