"Manual" calculation setting should not affect other spreadsheets
If a user has a spreadsheet that has calculations set to "Manual" (for what reason, I can't fathom), if they open that spreadsheet first, then all subsequent spreadsheets open in that session will do manual calculation.
Calculation settings should not be global like that. If you have to have a Manual calculation spreadsheet, that should only affect that single spreadsheet -- not any others that may be concurrently opened.
This is a terrible design choice.
However the workbook is set - manual or automatic is the way it should open. Can you imagine if the print area changed back to the default every time you closed a workbook? Of if the column width changed back to the default? Hours would be spent re-fixing the workbooks.
I don't care if it is this way for 20 years. If it is then is already annoying for 20 years.
Charles Williams commented
The base problem is that Excel does not have a calculation method that only calculates a single workbook when multiple workbooks are open, so many calculation settings are global but set from the first visible workbook opened.
AFAIK Excel has always worked this way for the last 20 or so years.
Scott Crowder commented
This appears to be a new behavior with the latest update. Was the change intentional or is ignoring the spreadsheet level recalculation a bug?