Thanks for that Ghacks article link, as it's quite thorough in explaining the control of this feature under Firefox and also includes links (which I did not follow) at the end discussing it for Chrome.
Both this article and one I gave a link to several days ago show that for Chrome this feature is rapidly coming up on one year old and is around 8 months old for Firefox. Because I don't allow push notifications I do not know what either browser has as its default setting as far as handing these off to Windows for presentation. But if you (any you) suddenly start getting these via Windows and don't want them presented that way you'll have to tweak your browser settings to disallow pass-through and/or turn off permissions to receive push notifications from the sites where you've allowed them to come from in the first place.
Brian - Windows 10 Pro, 64-Bit, Version 1903, Build 18362
The color of truth is grey.
~ André Gide