I see ship names as community folklore more than theory, but yeah, theories absolutely shape them. For Deku and Uraraka, 'Izuocha' feels like the baseline, the canon-compliant tag. But theories spawn the more specific tags. There's a whole subset of fics tagged 'Green Tea' that play with the idea of their relationship being a calming, steadying force for each other—less about explosive drama, more about quiet support. That's less a plot theory and more a character dynamic theory.
Then you get the angsty, future-focused theorists. The 'Deku's Successor' or 'One For All's Weight' tags often come from theories about Uraraka eventually sharing the secret or bearing the emotional burden. Those fics explore a theoretical narrative endpoint, and the ship name morphs to reflect that. It's fascinating how a speculative idea can become a whole sub-genre with its own naming convention.
Ultimately, the ship name becomes a signal. Clicking on 'Izuocha' might get you fluff, but clicking on something like 'Zero Gravity Heroism' tells me the author is probably working with a specific theory about how her quirk evolution symbolizes their partnership.