The 'Quick Filter Bar' toolbar is identical to previous versions.

When you type into the 'Quick Filter' search, it auto starts looks for possible matches as you type according to whaterver filter you have enabled eg: Subject Body But those matches will only be in the selected folder.

Are you by any chance entering text and then clicking on the 'Return/Enter' key ? If yes, then that means use your current search data and auto apply to all folders and so invokes the 'Global Search'. It's a quick method to apply current search data to more than the selected folder without the need to reselect a different search and enter all the same search criteria again.

There is no need to press the Enter/Return key in order to start search in Quick Filter - it auto looks for anything as you type. Pressing the Enter/Return key means you want to expand the search to all folders - aka use a Global Search.

I discovered the culprit is actually the addon "Expression Search - NG" I disabled that add-on, and that extremely intrusive "history" pop-up goes away with it. And the Quick Filter works the way it always did...