That sounds like a stretch even by EU standards when a acting openly envious. Google can warn or ban their misbehaving users for repeated spam violations. They can't ban people on other people's domains. "Legitimate addresses" can still send spam and it could have been caused by ignorant users who think "junk" is for non-immediate deletion and use it to keep their inbox tidy. In fact they /did/ deliver it but prefiltered.

Even if they could kangaroo court it for standard business practices they wouldn't since they don't want to be known as "the dumb fuckers who banned domain based spam filtering" and face pressure from annoyed constituents now receiving piles of spam.