I am not an expert on these things but I have heard it said that many larger retailers source their seeds from the same suppliers, so if there were a duff batch then many retailers may have the same problem.
Being a nasty suspicious type, if you were a cartel global oligopolist seeking to wipe out smaller independents, one strand of your destructive wave would be to ensure they had quite a few batches of duff seed to put negative thoughts into customers’ minds. I always instilled ‘check the merchandise’ into my juniors when I was a cancer researcher at the bench: duff products costing £200 were as common then as duff seeds costing £2 are now!
As ‘garden centres’ seem to be selling less and less stuff for growing vegetables and more and more bird tables, sheds etc, it may well be that margins are barely justifying floor space occupied…
Does beg the question whether an equivalent to ‘Which’ could valuably batch test seeds for Uk domestic growers….