Could you quote which paragraph you're talking about?
AFAIK, interoperability with C++ code is just one of their explicit goals; they only place that as the last item in the "Language Goals" section.
[0]: https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/...
[1]: https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/...
It's slow and sluggish, riddled with dark patterns and annoying pop ups, disrespects the user in every possible way, and hides basic editing functionality behind subscriptions.
The trashiest piece of crap software. It's up there with MS Word (which gets progressively more bloated on Mac).
Edit: Added "software" after crap for clarity.
I once found that a PDF file created with OnlyOffice displayed as intended on Chrome, but its embedded font couldn't be recognized or rendered correctly on Acrobat.
I keep Acrobat installed only for verifying the integrity of the PDF files I've created.