I see lots of examples of unnecessary hyphenation in phrases like "when she was five-years-old", is there a change in usage, or is it technology?

Obviously, at least to me as a native speaker, "when she was five years old" doesn’t need any hyphens, any more than "when she was five feet tall" or "when she had long black hair", but I’m seeing the hyphens used in lots of online writing, for example this article has

He never read the diaries, but he held on to them so that he could return them at graduation and have his students look back at what they were like at 12-years-old.

Again, my instinct as a native speaker is that we only need the hyphens when we make "five years old" into an adjective: "she was a five-year-old child".

Someone has suggested to me that it may be some grammar checker, like Microsoft Word, offering it erroneously as a grammar change. But surely journalists for major online outlets aren’t writing in Word, and aren’t taking its grammar suggestions if they do? Also my version of Word doesn’t suggest any change to "five years old" when I run a grammar check.