I think Adam Silver needs to step in at this point. He can be that neutral third party as to whether additional compensation is warranted.
Quick question, I could be wrong, but isn't surgery up to the player and not the team?
exactly. This is a rare situation where medical diagnosis vary by doctors post trade
Have you ever bought a house? Let me explain how it works. After you agree on the deal, you typically run an inspection. For all practical purposes, if you're not satisfied with the results of that inspection, you can back out. The seller can't and won't try to prove to you whether your concerns are warranted or not. Isaiah Thomas' physical is the same thing.
To use your house example. This would be like the seller saying the roof needs to be replaced. The buyer acknowledges the roof concern and agrees on the deal. The buyer still needs to go through with the inspection for the loan. Then the buyer backs out of the deal because the inspector tells him the roof needs to be replaced.
To extend the house example a bit further, I guess it depends on whether the seller told you the roof needs to be replaced, or could be fixed and you could still live in the house while the repairs were being done, it would just be a bit inconvenient, and here is approx. how much it would cost. Building repairs and their cost, like injuries are rarely black and white.
For roof replacement, read IT needs surgery. For roof repair, read IT has an injury that could delay his season. For the cost of repairs, let's assume the Celtics gave them IT's medical records.
My guess is that the Celtics said the roof needed to be fixed, and the cost of fixing has been factored into the house price, but the Cavs did the inspection and are saying it can't be fixed, it needs to be replaced at additional cost. The quibble is about that "additional cost".