Unfortunately, the post doesn't very well substantiate this claim. Can someone answer this StackExchange question, and if the answer is 'yes', can they also please substantiate their claim with reference to specific sections of the HTML5 specification in a precise way?
No, some tags are not supported anymore. e.g. < menu > https://www.w3schools.com/tags/tag_menu.asp
The current HTML specification has no "5" in it. HTML5 is just a buzzword. So you need to get the version number out of your head and realize that the same people who create browsers are the same people who write the specification and the specification they follow is the current one I linked to. That specification includes elements that have carried over from "HTML4" because they are current and supported. If and when they lose support, they will be listed here.