No. If he did work at home (which is what I'm assuming you mean by "fully remote") on classified material it was not part of his job, and thus if he billed the US Government for that time it would be timecard fraud. If you have knowledge of this, you should report it to DCAA ( https://www.dcaa.mil/ ).

My recollection is that Snowden worked in remote/satellite facilities such as the Operations Center in Hawaii (https://en.wikipedia.org/wiki/Kunia_Regional_SIGINT_Operatio...), but not from his house.

For all practical purposes it is true that classified work will not be done at home for a long period of time -- because doing meaningful classified work over a long period of time requires connectivity to a classified network, which requires a bit of infrastructure and the relevant accrediting authority has stringent requirements for this kind of thing.

I've personally participated in the accreditation of on-site SIPRNET (which operated by DISA at SECRET//NOFORN) enclaves and it is an expensive process that your company will not pay to have done at your house.

In addition, there would need to be daily audits of the security records for things like vaults, rated security room (even without open storage), and a vault for the Type 1 encryption device (which needs its crypto keys updated regularly) -- at the least -- which connects your (or really DISA's leased line) to the peer.