Here's a discussion of this from the installer's point of view, with a fair amount of chaff mixed in, but still some references to how some jurisdictions have been behaving:
https://teslamotorsclub.com/tmc/threads/santa-clara-county-retroactively-changing-ess-rules.189387/
One of the issues is that heat alarms listed to the smoke alarm standard are all 135F alarms (e.g. First Alert HD6135FB). There are plenty of purely mechanical (bimetal) heat sensors rated at 194F (e.g. System Sensor 5604), but they just close a pair of dry contacts when heat is detected. So without an alarm panel, I don't think they can be used; I haven't found a smoke alarm product that supports a remote sensor or provides a pair of contacts that could be used to initiate the alarm. Perhaps allowing a simple standalone circuit of power supply, horn, and mechanical heat sensor would be "reasonable."
The First Alert HD6135 FB manual says not to install it "where temperatures are regularly below –20º F (–29º C) or above 115º F
(46º C)". So if one could log the temperature in the proposed alarm location to provide some confidence that the temperature would be within the above range, that would be "reasonable" in my opinion, even if the listing standard mentions 100F (I haven't checked the standard). Some flexibility in mounting location would help with that, e.g. if the ESS is wall mounted, putting the heat alarm on that wall, but lower than the typical 12" maximum height below the ceiling, where temperatures may be cooler than near the ceiling.
Another option would be to condition the garage with a small through wall heat pump. Obviously that's a potentially heavy requirement for a project, but should eliminate the concerns.
Cheers, Wayne