I believe those are too wide, TK tried that 2-3-2 layout in their so called premium economy "comfort class" and failed.

UA could have used those crew rest seat in Y (17, 18, 19 HJ on PMUA 777XC 23xx or PMUA 3 class 763 13, 14 AB) as premium economy seats. If you have sat in one of them, those seats have legrest and 3 times more recline than Y.