Yes, I think it happens quite a lot in 4-board international team matches. As captain in two World Seniors Teams events I have seen quite a few matches reduced to 1 or 2 boards after an hour or less, whether or not by pre-agreement, more likely after the opening moves before games leave "book".And has a team match ever been reduced to single combat in this way before?
Though I never proposed it, or had it proposed to me.
Technically no conditions can be attached to a draw offer, e.g. "I agree a draw if your board 3 agrees it". See page 27 of the Arbiters Manual (comment to Article 188.8.131.52).
I think this is happens in Olympiads too in non-critical matches.
The team that is outrated is perhaps happy to get 1 or 1.5 board points (and probably some rating points) cheaply.
In the last World Senior Teams 65+ there were a few matches between German teams that were over 2-2 after 5 minutes. By the time I got to walk around, all players had left. Of course Seniors are more likely to be keen on a day off.
This case is a bit stranger. Maybe the losing player blundered so early that the captains or players just agreed to draw the other games but yes it does seem more likely that one of the players refused to be involved in a package deal.
The competition rules do not allow captains to agree results over the heads of their players, though perhaps in the past that was possible? They can ADVISE not COMPEL (FIDE Competition Rules 12.5 but I believe a new set of rules comes into effect in July; I have not seen the wording.)