Yes, if the team offers ice it's a conflict of interest even if they tell players "Hey, this is optional and we don't expect you there."
Fringe players are going to assume that the team's going to be aware, and that it will cloud their decisions. "Hey, that Johnson kid's always working - he showed up to that optional skate over the holidays even". And even if they say that they aren't, this would be in the minds of staffers. Behavioral Economics 101.
It's a moot point anyhow, since this rule has been collectively bargained by the league and the players' association. It doesn't matter what we think - the teams agreed to it, and the players agreed to it.