You could consider this type of library OS even more tightly bound to the application than your typical JS app as its actually linked to the user code.
If you define the context to mean it and then assume that everyone agrees with your implicit context, then maybe. In reality, OS and schedulers are not the same thing.
It’s also a leap from the “MacOS 9 was not an OS” GP position.
That wouldn't be the first time I've heard that statement, even among classic Mac enthusiasts.
Here are 3 definitions from 3 different sources: https://www.wordnik.com/words/operating%20system . Not a single one even mentions process scheduling or anything to exclude MULTICS, CP/M, DOS, or any version of MacOS or Windows. I know that some people think that being contrarian on HN is cool, but this is beyond ridiculous.
That's essentially what OS is: some bootstrap, scheduler and some APIs for developers and some drivers.