They may be, but there is nothing they can do about it. They can't lower the number of employees required to trigger the requirement without Congress changing the law..................
Every entity that has common controlling interest in any number of entities is considered as an aggregate of the entities they control. No matter how you slice and dice the companies they have common ownership and are considered as one for almost all legal purposes including health care head count I believe.
He who has the gold makes the rules. If they want to aggregate they can and leave it to someone to prove them wrong and stop them. Try it. See what happens.