Ah, yes, iPad Safari has the same problem but no option to show the tab bar with a single tab. If you hit the "show tabs" button in the corner you can drag it back from one Safari instance to the other, but it'll open up a new empty tab to replace it. You have to take the other copy of Safari back to full screen (to separate it from the new copy) and then use the app switcher to kill the accidental one.

I don't love this either, it's my biggest complaint about iPad's multitasking system.

The thread you are replying to involves macOS.