I agree with you. 80ohm's highs are not veiled (to my ears).
It's relatively easy to reproduce highs with headphones than lows and make people feel that the sounds are crisp & clear by accentuating the highs because they'll surprise by the detail they can hear that they couldnt before. After getting used to that world of headphone sound, 80ohms can sound no highs. While there's a grain of truth to that, I find that 80ohms has a very "soft" highs, but it's definitely there.
I notice that both 80ohms and 250ohms reproduce acoustic guitar sound very well. My dad plays guitar, and I have many experience listening to it, and the acoustic guitar sound, its subtleties/nuances that dt250 reproduces/delivers sound very real. Vocals, in contrast sound just a little cleaner than actually having someone singing in front of you (but no by much, really just a little). I remeber reading in this thread that people commenting 80ohms as having forward mid, and maybe my vocal sound experience is one example of it.
I also had to exchange dt250/250 twice to get a good unit. They happened around serial 68000, but like donunus says, it may be just Beyer thing.