When in the tabs view on mobile Firefox, where you can:
currently when finishing those actions ("Tabs sent!", "Private tab closed" messages briefly show), the tabs view closes. And you end up with the browser view.
For the first you lose the selection of the multiple tabs. Where I usually then just want to close those sent tabs. I have to go back to the tabs view. Select the same tabs again. Then close them.
If the tabs view had stayed open and the tabs selected, I only would have to click the 3-dots and "Close".
And for the second, when I close the last private tab, I usually want to go back to normal tabs. But the (empty page) private browser view is shown. I need to go to the tabs view again, and switch back to the normal tabs.
If the tabs view had stayed open, I would immediately be able to switch back to the normal tabs.