SR is for when you accidentally installed MMF really.

Except, no, you can run (single lambda, not muxed) LR transceivers on MMF, it's out if spec but you actually get around +20% range before hitting dispersion limits.

I'll also note SR ranges are not in fact long enough for larger buildings. And this gets worse with higher speeds, since modal dispersion is a bandwidth problem, not attenuation.

Also, using 800G for comparison is a bit ludicrous ;). 10G is bread&butter, 25G/100G is mainline. (40G is the shunned weirdo uncle.)