A "bad look" is legally irrelevant. A US citizen has an almost unlimited right to enter the USA carrying anything that's legal to import. Blank phones are legal to import.
Carrying a blank phone is much less suspicious than carrying a locked phone that you then trick border officers into wiping all the data off of.
I agree that it's legally irrelevant, but we've seen many court rulings lately where legally relevant things are ignored (e.g. 'the president is immune to any legal repercussions from committing crimes') so given the current political climate I think 'bad look' is still relevant in practice.
