Lookie here:

When switching off a warrior with the "Titan's grasp" perk, the item in the offhand should stop working, since the player character can no longer wield a twohanded weapon alongside any other weapon or shield. It doesn't though.
The passive stat boosts from the Thornshield stay active when it's equipped and so do its combat effects continue to be applied.
It wouldn't surprise me much if this might also be the case with any other item equipped in the offhand slot when switching off warrior.

When switching off a warrior with the "Titan's grasp" perk, the item in the offhand should stop working, since the player character can no longer wield a twohanded weapon alongside any other weapon or shield. It doesn't though.
The passive stat boosts from the Thornshield stay active when it's equipped and so do its combat effects continue to be applied.
It wouldn't surprise me much if this might also be the case with any other item equipped in the offhand slot when switching off warrior.