I thought that, too but on second reading, I think they want text to be expanded they didn’t type. IOW, they want “IOW” to be replaced by “in other words”, even if it appears in email messages they receive.

A way to do that would be with a font that has ligatures for abbreviations you want to see expanded, but that would only work if you can control what font applications use (in theory, replacing all fonts on your system by ones with ligatures would help, but that already wasn’t very feasible before Apple locked down the OS)

I also think they would want something more intelligent, as many, many abbreviations have multiple expansions. They wouldn’t want to see “in other words” if the writer meant the Chiwere language or “isle of Wight” (https://en.wikipedia.org/wiki/IOW)