Update:

I ended up calling United after a week or so of waiting. UA rep seemed confused, "you have been ticketed and are in business," tried to explain that from Copa's side, I was still in Y. She offered to call Copa and did, confirmed I'm in business... I noted I can't reserve a biz seat online (can only reserve Y), she said when I check in/get to the airport I should be assigned a correct seat. This trip isn't in several months. Sounds like I'll be fine but it's just unsettling that I have a seat reserved in Y...