For those not located around military bases with radar systems, that's probably true. My car's remote was rather deaf in a local mall parking lot and worked perfectly well a block or two away. I traced it down to a local restaurant which was using a wireless order-taking system which was operating on 433.92 and was clearly not complying with Part 15 - its central node was polling the remotes 2-3 times per second and exceeding the Part 15 unlicensed-device duty cycle limits by a factor of Many. Its power was also probably excessive - it jammed the car remote hundreds of feet outside the restaurant walls.
There have been quite a few reports of garage-door opener failures in the vicinity of certain military bases. The military is the primary allocation-holder of the 420-450 band - hams are secondary and subject to "noninterference to primary user, no protection against interference from primary user", and Part 15 is at the bottom of the heap.
Getting a 433 MHz garage-door opener to work properly anywhere near Beale Air Force Base, or other PAVE PAWS or similar radar sites, is probably going to be very much a hit-or-miss proposition. Those are pretty powerful transmitters.