e2e encryption is not trying to solve the problem you describe. If I'm going to open and view private notes on a non-private machine, no amount of encryption will help me.
I think the parent has a valid point in that terminating the encrypted channel at the device level leaves a pretty gaping hole in the not so rare event that people are forced to use employer provided devices at least some of the time.
There's a reverse issue as well though. It may well be the intention of employers (or even a legal requirement) to stop employees from syphoning off company data through some encrypted channel that IT has no control over.
So in some cases the assumption you're making that device = user may be an unavoidable compromise.
Some local note apps store them in dbs that would require auth, etc.
I just think this is a huge pitfall of using markdown notes.