I googled this issue and landed on this page, I find it quite alarming to see this popup which bakes the question:
"Have Microsoft been monitoring my keystrokes, passwords, and any other keyboard related activity whilst outlook was open in the background since I installed Office 2016 more than 2 years ago?!"... I am extremely annoyed for seeing this...
I think the most sensible way is to ask this question to the people who developed these apps as Apple are now being nice by warning you that this is actually happening on the new OS...
... I think Microsoft has a lot to answer ...