My anecdotal observations are that this often causes extreme number of tabs. I've seen multiple examples from social media in the last month of people scrolling through their mom's (/little brother's/etc) phone, showing hundreds of tabs, but usually all duplicates of the same dozen or so. I remember seeing similar things firsthand (but not to as great an extent) when the first generation iPad came out. And I've also witnessed the same in offices, where doing something in an app or an existing page will arbitrarily open a new window or tab, leading to an explosion of windows and tabs all hidden beneath the IE11 icon in the Windows taskbar.

By all signs, it seems true that (a) average people don't know what tabs are, and (b) they have a lot of them. So it makes me wonder about your methodology. I used to be a Mozillian, and I remember the less-than-rigorous excuses that Firefox UX folks reached for when backfilling justifications for their design whims.

Honestly this is the only reasonable way to use tabs on a mobile browser. There is almost no drawback of keeping them and closing them is a chore. I get it sounds like the typical "boomers using the internet" but given that you should expect old inactive tabs to unload anyway having even hundreds of tabs open is a detail.

That said, what you're saying is, "In practice, users don't have a lot of tabs open", which is very different from what I was responding to, which was "users shouldn't have a lot of tabs open".