Home made mayo is shelf stable. PH should be down around three. It’s the grocery brands that try to smooth out the tang and increase the PH that makes it need refrigeration. It sounds insane that egg yolks and oil don’t go bad on the counter if you add lemon juice but that’s about the extent of it.

That’s not to say it doesn’t degrade much faster and honestly, mayo need to be cold or it just feels like sandwich grease :)