It could just be the site has very valuable content, and the algorithm is ignoring the “bad parts”. Each case is different.
It just wouldn’t make sense for google to rank the crawler version as if it was the JS version. (in the general sense)
There is no menu , no suggested topics, no gutter links, user profile/badges pages are noindex , and a boatload of other features that are just not available in the crawler version.
I’ll update with a new topic once the results are in. So far the positioning in the SERPS is very erratic
edit user profile/badges pages are noindex via headers