I kind of felt that it was "unconfirmed" confirmed in X-men 46, in 1995, when Iceman and Jean were book shopping - he was wearing some fabulous magenta pants btw - and something came up about Jean being a Telepath, Iceman saying something to the effect of "so you know"...and Jean replying that she had absolutely no idea what he was talking about. At the time it could have been inferring the problems he was having using the full extent of his powers, but that scene more than anything had a lot of subtext. Sorry I don't have the scan, I tried to find it online but google is not my friend tonight. So yeah, the fact they wrote him with this idea in mind is not a surprise at all.