Could one have two white bishops after promoting a pawn?

Yes it's theoretically possible to have two light-squared bishops due to promotions but so exceedingly rare that I think most professional chess players will go their whole career without ever seeing that happen.

Outside of playing a game for piece value? No, not really.

In this case, of course, someone moved their bishop from black to white and their opponent didn't catch it until awhile later.

Promoting to anything other than a queen is rare, and I expect the next most common is to a knight. Promoting to a bishop, while possible, is going to be extremely rare.