Yep.

It can come off as a logical conclusion to most people never using anything but web these days.

Desktop OSes are not suited to running untrusted code, unfortunately, so you want to run as much as possible of your closed source megaco software in the browser

Well, not. Browsers are slowly becoming the cross platform for your apps and it makes a ton of sense from resources (create a single app vs an app per platform) perspective.

Not really. Browsers were one of the first pieces of software to do sandboxing, but now virtually everything uses sandboxing for organization and security - Android apps have a permissions manifest so they can be sandboxed. Amazon cloud servers are mostly Kubernetes clusters, which is just sandboxed virtual machines. ChromeOS already is a OS/browser hybrid with native sandboxing (and the short lived Firefox OS. Running a 32 bit app in a 64 bit environment requires a compatibility layer, which is a sandbox. If browser technology has already been pushed through the OS stack, why not complete the loop.

The main use case for hardware acceleration is progressive web apps, which is literally a plan as old as 2006 to make browsers able to securely run signed code natively (as an alternative to using extensions like ActiveX, Java, Shockwave, etc, all of which were notoriously insecure).

So honestly, I don't think it's a dumb idea at all. It would honestly be kinda cool if I could go to blizzard.com and just launch a game full screen, securely with a simple approval rather than downloading and running a separate launcher app. (Assuming the implementation was otherwise sane; I know the current environment of enshittification could torpedo the idea entirely)