Tim hitting on Bruce would be infinitely less squicky. He's got twice Cass' maturity, a dozen times her understanding of the world, and less than a thirtieth of her dependence/obsession/fixation on Bruce as the ultimate end-all and be-all of her existence.
Now, the issue starts with this, so it seems likely to me that Horrocks was trying to repeat that motif; Cain being perturbed by Cass trying to show affection, and then Cass repeating the attempt with Bruce and having that affection returned. I can't fathom, though, that he would have missed the fact that it comes across blatantly sexual, even before Leonardi drawing in the suggestive poses... between the age difference in the two scenes and the fact that the arc immediately prior to this one was the "Cass' sexual awakening" one, not to mention the simple context of the way Babs presents that insight, there's pretty much no innocent way to take this. Either Horrocks did it on purpose or he's staggeringly blind as to the connotations of his scripting.