Whether or not they have probable cause is a matter for the courts. Polite or not, you're dealing with individuals who have little to no oversight and even if they do something illegal they often don't have to answer for it. The moment to insist on probable cause and reasoning is afterwards. Let them rack up their bill first.
I'm not sure this is necessary, my five button mouse worked just fine on the mbp my work forced me to use in 2020. The only issue was pointer speed is wonky, and the scroll wheel is intentionally stupid.
But the buttons work like Linux uses them, not like windows uses them. Which is fine, but I can see how the uninitiated would have a problem with that.
As a weeb living in South Carolina, I feel bad for Japan.