Outgassing occurs with petroleum based greases mostly. The modern lythium based greases have a lot less of that.
Yep. I've used '50s lens for 40 years, no problem. Seen lots of old lenses with no problem. Some lenses (made by EVERYBODY) have a tendency, after many years, and possible storage issues, DO have the inevitable degradation of the lube.
Linking the issue to Leica lenses, however,
is due in part to the Internet Echo Chamber,
and Rabid Leica Deniers.