I don’t know how much Yakima mounts may have changed over the years. My Yakima rack is close to 30 years old. I can say that on my rack, the locking mechanism is purely cosmetic. The little “lever arm” that is used to tighten the screw clamp is made of plastic and the part which engages with the lock is just a little molded-in “U clip” which is thin and delicate. Anyone who owns a medium-sized screwdriver has “all the tools necessary” to pop that lever arm free of the lock. Popping the lever arm loose with a screwdriver would actually take slightly less time than unlocking it with the key.
I never remove my Yakima rack, but that’s because I’ve customized it with side bars connecting the front and rear cross bars, and this adds greatly to the time needed for assembly/disassembly. I can’t recall for sure, but I think the carpet padding attached to the cross bars must also be partly removed to disconnect the mounts on one side (just for the first side to be disconnected, not both). The side bars are a loading aid in certain situations, and more frequently are used as a mounting system for auxiliary bars of greater width for carrying two boats (so I don’t have to have bars of greater width on the car when only carrying a single boat), and in that case they also increase the spread between front and rear bars by about a foot. I also use the side bars as additional anchor points for rope for stabilizing various boats that might be carried (though I have home-built gunwale stops I can use when the auxiliary cross bars are attached). Anyway, I figure that the greater complexity from rack customization is a pretty good theft deterrent, but I never shy away from pointing out how utterly stupid the design is on Yakima’s “anti-theft” locks, which are just about the silliest imitation of a functional lock that ever existed.