Yes, I agree. All people under 60 should avoid a 3rd jab based on that thinking (apart from my relatives and people I like).
The benefit does seem to be that it’s providing greater protection against infection. Anecdotally, perhaps nothing additional against illness.
In my circle, I’ve now got 12 friends and 4 family members who have been “infected” since Christmas. I’ve been around all of them prior to them testing positive (but we’re presumably infectious) and managed to escape it. So has our one mutual connection who is also triple vaccinated. Of the 16 who have gone down, two reported symptoms (that would have been ignored had they not known otherwise). All of them only double vaccinated.