If I go to Control Panel > System, it says indeed 26100.3915.
But the Windows Update > Windows Insider Program still says 26100.3909. It does tell me it's up to date, however (in Release Preview channel).
Update: That problem is now resolved (by Microsoft - I did nothing). The proper version shows up now in Windows Update.
The notifications? I keep trying different switches, thinking maybe there are new dependencies that are unclear. They still don't work. On rare occasions, I get one, although it's been many days now since the last one. Then nothing after that.