It was explained...but considering that Mysterio was apparently a key part of the alleged coverup and is actually Kindred's whipping boy, plus we know now that Kindred can influence people's minds, add to the fact that the resurrection coincides perfectly with Brand New Day while Kindred clearly has some kind of demonic powers and interest in keeping Peter & MJ apart - he literally set things up so they'd be separated right when Peter was seriously considering re-proposing.
I mean, it seems like if it is Harry that Spencer is going to do for him what he did for Kraven - address a poorly-handled resurrection and recontextualize the character. Now whether that involves him dying again is up in the air.
Because the BND resurrection was basically part of the plan to roll Peter's world back to an imagined past when he was a swinging bachelor hangin' out with his best pal Harry! Never mind that Peter was a serial monogamist, the good old days are back! Whereas if Harry is Kindred, it means he came back for a purpose. He's not really done much of anything to justify undoing Best of Enemies since he came back, to my knowledge. Kraven got his stuff in Unbeatable Squirrel Girl (although I'm pretty sure that's not what the writers of Grim Hunt had in mind when they resurrected him), and the Hunted.