> it leads to "managing" them later in bookmarks UI to find+reload+delete them

I agree. There is definitely less UX friction with tabs, and I can live with 20-30 (50 maaax) and only some of the time. But 100 ephemeral and much more? most of the time? IMO this is just unwillingness to improve the system. You can definitely get less friction dealing with most of them as organized bookmarks than wild tabs.

> tabs already have the HTML downloaded and visually pre-rendered

Most new browsers purge tabs from memory, so the instantaneity is not there anymore.