Middle of a pandemic in a season that shouldn't be happening and he's worried about the cut he's gonna get this offseason. Unreal.
Boras is not a good guy by any means, but the only language the owners and Manfred speak is $. They certainly don't speak the language of compassion.
By saying that the quarantine rules get in the way of his players ability to work out and remain ready to earn their contracts he is implying that there could be a lawsuit over this as follows:
League asks players to play under circumstances that will get them sick
Players get sick and have their lifetime earning potential appreciably diminished because they are unable to work out because of the regulations of the same league that let them get sick in the first place
So the league / teams can be sued for the difference
I can't imagine that law suit actually occurring, but it looks to me like Boras is using his evil super villain money manager powers to protect the interests of the players he represents, at least in this instance.