This is Snowden's claim and it's not implausible, but it's also quite a coincidence that he'd end up in the top country for spying on the US it's also possible that he wanted to be in Russia and simply made up the part about it just being a stopover. If Snowden was looking for asylum, there are several other countries that don't extradite to the US. I can see why he'd temporarily be stuck in Russia, but after several years he couldn't find any other way out? There was apparently a privately-funded attempt to get him to Iceland, but the last update on it was that they were in contact with a "third party representing" Snowden...and then nothing.
A third fact (in addition to Russiabot Greenwald's involvement) that makes it questionable is that he eventually applied for Russian citizenship in 2020. One explanation is that he could do this to get a Russian passport and fly somewhere else with no US extradition treaty, but he hasn't chosen to do so yet.