These days "tandem rated" or "tandem specific" terms are somewhat meaningless. If the concern is to find heavy duty usage components, then you might want to take a look at the "mtbtandems.com" or the Facebook group:"mountain bike tandems". Very large group of hard core single track tandems riding boulders, dropoffs and just about everything in between (super tight switchbacks are the bane of tandems). A majority of thru axle tandem wheels are now being build with DT Swiss e-bike hubs and straight pull spokes.

Probably the best QR tandem hub made, is no longer. Chris King has stopped production of their tandem hubs and from my recent parts search, there is no remaining stock anywhere. However you can order up a run of 100 and they will produce those again.