Agreed No self respecting airline would willfully downgrade a revenue pax. Providing elites seating in premium cabins which are not sold on routes but turn up in inventory due to EQV is another matter though I've not seen it happening frequently on either airline, in fact happening at all... I've seen in once on Qantas that's it.

Conversely, I've seen BA fly an empty F cabin (zero sales/redemptions) from LHR to GRU with no upgrades. I've seen this all the time on LH DEL-MUC.
But with one upgrade redemption, as the only pax, I've gone F from MUC to GRU with a full First service!