Mac Excel 2016 suddenly requires VBA addins to be installed addins, not just loaded from startup/exc

A recent release of Excel 2016/365 for Mac has stopped opening .xlam addins in startup/excel and started requiring that the macro be installed as an addin. PC version has no such requirement for xlstart or altstart. 

Plus XL for Mac seems to need to be updated every week. What's up with that?