I agree with this. What I'd say further is that if you're a generalist, you're not really in a position to pitch yourself as such. You either need to build a relationship with someone who recognizes that you can have some non-traditional role, or you need to spin your experience to someone who's looking for a specific skillset. Telling someone you're as good at some specialist thing as people who are specialists at it comes off as bad and falls as flat as calling yourself a polymath (or any of the other phrases people seem to come up with)

Pitching "I can do anything" doesn't work.

Most disciplines are ~ infinitely deep. An amazing jazz upright bassist once told me that he was only scratching the surface, and to look into 5 other musicians for examples that were blowing his mind at the moment. A flight instructor at one point said "You'll think you're competent at flying but a pilot can sense your ignorance a mile away with a couple sentences." I don't know what constitutes polymath but I can barely be a mono-math and I am happy with what I have.

Yet polymath doesn't even mean "good", it means Jack-of-all-trades (master of none.) If you want to say "aspirationally a polymath," that might go down easier. Still, you need to be in a rare corporate body that understands the value of your broad, shallow pond of knowlege, not having the average institution hire you and then not value what you bring.

Where appropriate, I use "geek of all trades" specifically to avoid this.