Recent builds of Excel 365 (version 2308 onwards) have introduced a change to the way Sheet Calculate (Shift-F9) works.
Previously Sheet Calculate did a recalculate of all changed and volatile cells on the selected worksheet(s), but did not marke these cells as having been calculated.
Note that this only gives you “correct” results if all precedent inter-sheet and inter-workbook dependencies have already been fully calculated, and that cells on other worksheets that are dependent on the sheet(s) are not recalculated.
After a sheet calculate the formulae in the sheet, the sheet and the workbook are flagged as uncalculated (CALCULATE shows in the statusbar), unless there were no uncalculated or volatile cells.
In Manual calculation mode this meant that if you did another Sheet Calculate the same cells got calculated again.
From Version 2308 Sheet Calculate resets the dirtied and uncalculated cells on the calculated worksheet(s) as having been calculated and hence clean.
Excel and UDF Performance Stuff 