Bell said himself hes reporting during the week 7 bye, coming back for week 8 and will give it his all. Link doesnt matter since you dont believe the source, but thats whats been said. Id think he would have refuted it by now if there was some huge conspiracy and they are just lying.
Bell did not say it himself, not anywhere on public record, anyway; the ESPN article quotes Bell saying only that he will play this year -- the week 8 date comes from a "source," identified separately in that same article. I will gladly stand corrected.
In any case, at this point we're basically just quibbling about whether Bell reports week 8 vs week 10, when he was expected all along. So as it relates to the OP, do those two weeks really make a difference in his value, or rather in Conner's value? Even if Bell comes back next week as rumored, I think Conner gets CLE & probably BAL to himself. That means JAX, DEN and LAC will be a timeshare for both guys, and those are kinda ugly matchups anyway. So if Bell doesn't show up 'til week 10, Conner would at best be a borderline RB2/flex play, still. OAK and NO in the post-season are about the only bright spots left on the schedule, but you can't trust either guy in those most important weeks of the season.
So the take home I'm seeing here is basically: sell for whatever reasonable value you can get for either guy, right now.