Basically, the only way this is enforceable is if you get caught from another charge or an accident happens and an officer has to handle your firearm. Example, you get into a car accident while CCWing and EMS takes you to the hospital. They will log that you were armed and when the police show up to handle the firearm and store it, they will eject the mag and do a round count. So if they count more than 10rds, then you're in trouble.
There is almost no way to tell if a magazine for a pistol is blocked if it's inserted into said pistol. Same goes with rifles like an AR mag. Unless you're using a mag with a window or a clear mag, then there is no way to tell how many rounds it holds, unless they do a physical count. Which means a crime has been committed, about to be committed, or you are committing a crime and HPD can take your rifle from you. If you willingly hand over your rifle to an officer, then you're a moron.
Now if your mag isn't inserted into your handgun, then you can tell most of the time if it's blocked or not. When I was in Vegas checking my gun at the hotel armory, I ejected the mag, but didn't have to remove all bullets.Security could tell it was a 10rd mag and made fun of me.
I'm curious as to how you've gone out of your way to avoid pistol mags over 10rds? No store will sell them to you unless you're LE. And all guns come with 10rd mags when you buy it from a store. Mags on the stands also are blocked to 10rds in stores.