In the past, yes, and you still could if you use old enough features, but nowadays browsers heavily restrict sites opened as just .html file. For example you could not use modules at all if they're in separate files.
That is at least until we get Isolated Web Apps and what ever the other proposals related to it alö called.
Is blocking access to local files a new thing? Considering the threat (you download a html file, open it in your browser and it tries accessing random files and exfiltrates them using JS), I would be surprised if this has worked in the past 10 years
That is at least until we get Isolated Web Apps and what ever the other proposals related to it alö called.