This is either a bug or a case of inconsistent behavior
Moving the pointer on the list changes its highlighted entry just like when using various keys - but only the keyboard has the power to apply the Filter without confirmation because mouse choice do requires also a click
So please make Everything by default behave in the same way when highlight in this drop-down list is brought to it by mouse pointer. And as it is happening now, pressing of
Enter
Left Mouse Button
I am using Everything 1.5.0.1341a x64 Portable on Windows 10 Enterprise 20H2 x64