Is this grounds for $100? No, for so many reasons...

First, the rule indicates you are only eligible for access during regular hours of operation. The hotel does not regularly operate the CL during holidays, so it's not regular hours of operation. The rule does not allow for access every week day, does it? Only regular hours of operation.

You were given this information at the time of booking, so you have the opportunity to stay elsewhere. The guaranty isn't supposed to be a "gotcha" for members to use against Marriott. It's supposed to ensure we don't have surprises when we check in. In your situation, there is no surprise.

Under your line of reasoning, every PM would basically get $100 off every time the CL is closed for a holiday. Clearly that is not the case. If the CL were closed during a regular business day, that might be a different story, but when that happens, hotels usually make other arrangements.

The hotel is willing to give you free breakfast, which is the remedy often used for when the lounge is closed. You cannot ask for compensation above that. You cannot refuse the free breakfast because you would rather have the $100.

If you do want to still make the rest of us PMs look bad by pushing the issue, you need to make the hotel aware of the issue when you check in and allow them the opportunity to offer you breakfast, which they already have done. This solves the issue. No compensation is required, not that they even really had to offer you breakfast, as it is NOT regular lounge hours anyway.