{Ctrl+W} -- 'Close file' or 'Hide column'

I have been issues with Excel lately, in that {Alt+F} or selecting File is taking longer and longer to display. (I usually have 20-30 excel files open, and it appears that something in the File Screen iterates through the open files in the manner of 1, 1,2, 1,2,3, 1,2,3,4, etc. -- not as bad as a n² or n! type of programming issue, but it's still extremely frustrating. ) To avoid this, switched from {Alt+F}, C to {Ctrl+W}. Today, Excel switched from {Ctrl+W} closing the file to instead hiding the column of the currently selected cell (s).

Is this MS being "helpful" and messing with functionality? Or did I inadvertently change a setting somewhere and break it myself?

Windows 10 Pro, OS Build 19045.6456
Microsoft® Excel® for Microsoft 365 MSO (Version 2603 Build 16.0.19822.20086) 64-bit