I have recorded at very loud volumes, but am not a proponent of that in a zealous way.
Ive recorded many a band live in the studio and the gear is cooking. You do have to have some volume to be heard with a slamming drummer. Also when the powertubes, not the pre amp tubes, are in the sweet spot you got some volume going on.
I wouldn't stick my ear down there. No way.
Just as i wouldn't stick my ear next to a snare drum to find the best mic spot.
Another aspect is performance. You have a guitar player substantially turn down his volume or change too much, watch his performance go to shit.
The levels and tone have to be in a comfort zone of the player to extract the best from them.
For home recording, I've used my trusty Fender vibro-champ many a time, but when that's singing, I wouldnt stick my ear next to that either.
Besides, the human ear, or should I say 'ears', hear things differently than a mic does for reasons previously mentioned.
Then we get to the whole input chain
All the different things that your 'miced source sound' goes through. Finally you hear it through your monitors which can vary wildly even though everyone claims that their product is flat.
Then we have that guitar tone having to fit into the context of the mix.
Lots of variables from the source to the final recorded tone.
So all I've been saying is why risk your precious eardrums by sticking them next to the speaker cone.
Work out your guitar sound by how it sounds in the monitors, which is it's final destination anyway.
Try different mics, try different positions, try adding some room mics, try dialing down the gain, try dialing it up.
Experiment, and learn what works for you.