tracking linux-firmware.git and backwards kernel compatibility

I've been tracking the upstream Linux firmware repo in /lib/firmware on a couple of machines, doing very periodic updates of that tree. I *think* I saw a firmware loading error booting an older kernel on the machine where I did a git-pull last week. Does that repository have a policy about backwards compatibility with older kernels, or is that a non-issue (e.g.) because all the kernel does is load a binary file onto the target device using a standard interface that probably hasn't changed since a long time?