HA...YOU don’t live in Oregon, do you? Compact is another euphemism for “green” or fuel efficient, and many parking lots have almost all spaces as “compact”...and, I DO NOT NEED a warning on where to park my Ford 150 pick up...
In northern Virginia, the "compact" designation is used to indicate spaces in parking structures that you DO NOT WANT to put your F150 in ... as it would be sticking out into the travel lane.
If one were to park a large vehicle in such a space, one would be most exceedingly rude, and at serious risk of having one's vehicle damaged.