After updates Excel doesn't automatically open all previously open windows!

Excel in Office 365 on Win10 seems to update very frequently, at least once a month it seems. I have always some one-dozen Excel spreadsheets open on my three 4k monitors at any given time. After the update, none of them is to be seen: just Excel itself has been reopened.

Now I have to go and reopen all these Excell spreadsheets manually. Why? Firfox for example manages to reopen everything by itself. There are third party apps that will reopen ALL previously open windows, regardless of what software (but you have to "save" the last configuration of your screens). If third-party apps can do it - why can't Microsoft? I would understand if there is some "privacy issue" - but then there could be a pop-up, asking: "When we closed Excel we also closed several spreadsheets. Do you wish to open closed spreadsheets on the next startup?" Plus: previously open windows aren't exactly a secret but can be seen in recent files anyway.

Not the exact same issue, but related:
I am dreading to update Windows 10 or otherwise shut down the computer for exactly the same reason: with startup, I have to manually open all Ecell windows again. There is third-party software that does that for you, but it's fiddly. Now in theory the solution should be: save all Excel spreadsheets before restarting the computer, then the last opened spreadsheets should be visible in THAT ORDER in recent files in Excel. Only: nope, I see other files, not the 10 that I last saved. I can find them in the list eventually, but the list seems not to be in the order of "last saved".