Yeah with Drouin back, this was to be expected. I'm sure people would rather have both play to bolster the offense to compensate for the loss of Stammer, but the Bolts want to tighten up their game and it comes down to roles. Coop has been trying to make the 3rd line into a shutdown trio, and I guess have the 4th be grinders. So it makes less sense to play him now if he's not in the top 6 or with other skilled players. A guy like Bluden, as limited as his skillset is, can fill that role and play within his game.
That's the thing, JAM is not good on defense, so he cannot be put on the 3rd line for a shutdown role. Cooper is going like you said with all true "4th line grinders" on that line now. To be honest, I don't see anything special with him in the top 6 , and obviously Cooper does not see it either. But with Drouin back, it is a no brainier you go with Drouin over JAM, to have them both in the top 6 would be a defensive nightmare, and with no Stralman or Hedman, makes matters even worse.