The results of the testing I did with these proofing tools were disappointing. Things that should have been flagged weren't and things that did not need to be flagged often were. Sadly, twenty-six years later in the world of Windows 10 little has changed.
In her marvelous Great Courses lecture series, English Grammar Boot Camp, Anne Curzan shows little love for the Microsoft Word grammar checker. She says that it often gets things wrong, and sometimes the rules it tries to enforce are often not even rules. (For example, on not starting a sentence with "and." She quotes Merriam-Webster’s Dictionary of English Usage on this point.)
I certainly have my issues with Microsoft tools. The Word 2013 proofing tools failed to flag a repeated "the." The grammar checker in Outlook wanted me to lowercase "give" at the beginning of a sentence (perhaps because it was preceded by "p.m.") and failed to catch a "you" instead of "your" when I used the phrase "your money."
Microsoft is not the only guilty party, however. The proofing tool for my personal blog has its annoyances. It asked me to replace "thyme" with "time" and "adobo" with "adobe." I guess it doesn't have much of an interest in cooking.
The bottom line: Don't put too much trust in the tools. Proofread carefully. Better yet, get someone to proofread your work for you.