I assume you checked MI law regarding what visitation is for summers or vacations is if there is no other court order to the contrary, and that it does NOT give him this time. Or that your initial decree fo divorce does not give this time by default if no otehr time is agreed to?
If so, then it's highly likely that he is just blowing smoke up your butt.
Here's the thing... EITHER he has a reason to believe he gets what he says he wants OR he is lying about what the FOC says. People are ALWAYS saying, "my lawyer says this" or "that"... but it doens't mean they'v eacutally even talked to a lawyer, let alone gotten that advice. A LOT of what lawyers do is to make clear that they did NOT give the wacky advice that their clients keep wanting to SAY they gave! The foolish stuff they have to do... the crazy questions when you see those lists... it's always because someone actually questioned it when they did othewise previously... like the series of questions, question "So, hwen you did the autopsy, was the patient dead?"... answer "are you sure you are smart enough to HAVE a license to practice law?" ... question, "how do you KNOW he was dead"... answer "his brain was in a jar on my desk. How do we know you're smart enough to practice law?"
Clearly... it sounds like the medical examiner is beating up on the lawyer, and it might be that hes' looking pretty smart here... but the lawyer in the grand scheme of things MUST ask these questions... if he did not confirm that the guy being autopsied was DEAD first, then the doctor doing the autopsy would be subject to all kinds of horrifying questions about how he confirmed this stuff... so the doc being mean to the lawyer about asking these qualifying questions is just being a jerk about preliminaries JUST to be a prideful jerk... not because it makes a lot of sense. The LAWYER sure knows that this stuff is pretty dumb... but they pretty much HAVE to establish it so the doc needs to answer the questions befor ethey can go on.
You'll see this when you get your law degree... lots of this stupid stuff that lawyers do is more to protect themselves or their witness than it is to really get the evidence to the jury... and part of that is because people like your ex say stupid stuff ... like that their lawyer (or the FOC) told them this or that or the other thing that was WRONG.
IF you worry that the FOC todl him something that was improper according to your interpretation, then why don't YOU just contact the FOC & explain the situation & aks what's up? WHY would they tell him that he could have a whole month unspervised? You'll probably find that they did NOT tell him that... or if someone in their office DID tell him that, then it was in error & the'll be backpedaling QUICKLY.
This is assuming your interpretation of the current orders in conjunction with general MI law and the decree is correct. If your interpretation is in error and there IS some way he can get tha tmuch unsupervised time... you may want to know this. Which is why you may wnat to call them... to get it clear.
Also, calling them might clue them into the fact that he's slandering them and claiming that they're saying things they didn't say at all... which might help you in the long run.