Most likely only if those small instances become hot beds for signing up for accounts to go cause problems

Sure, there are smaller instances that don't vet, but according to the beehawk admins, they aren't an issue in terms of moderation, probably because of their small size. If other instances were to cause an immense need for increased moderation, I'm sure they will defederate from them as well.

Also the admins made it clear that this is supposed to be a temporary action until they are able to effectively moderate their community according to their rules and goals.