Tab groups are a mental shortcut so you can spend less time figuring out the nature of the tab you're looking at or finding particular tabs.
If something automates their creation then there is absolutely an advantage to sites that can subvert the classification method, because users will start with the "banking site" expectation instead of no expectation at all.
Who has that many bank website tabs open? And that are still active, because of course bank websites log you out if you do nothing within a minute or two. And then create a tab group from those tabs, and then the bad actor correctly guesses which bank you use and has bypassed Safe Browsing (which also uses ML now) and you visit the tab and manually (because the password manager won't work) type in your credentials?
Worrying about this as a potential threat is on the same level as my bank "disabling" right click.
If something automates their creation then there is absolutely an advantage to sites that can subvert the classification method, because users will start with the "banking site" expectation instead of no expectation at all.