You're correct on the "in a designated flying position". Heck you can be grounded on a T Cat for several months, with "unfit flying duties" as a MEL and you still get AIRCRA (up to the 180 day mark...).
There are other benefits to being at the pointy end, aside from AIRCRA which I already broke down for LRP flying in Iraq/Syria as around 3 bucks an hour.
Financially, I always made WAY more money off Ops FSP/HA/RA and /or
the TD itself than AIRCRA will ever be worth. Speaking from a purely monetary perspective, even exercises were normally "pretty gucci" as we'd be on full per diem, in hotels, etc. One example, I went to Scotland for a month in hotels, lived well while there, traveled on non-flying days to castles, historical sites, etc. I maxed out my tax free amount of 'stuff to bring home' ($800 CAD), and I had money 'left over' when my claim was finalized. Exercise locations themselves are pretty gucci; UK, Sicily, Norway...
I seriously lucked out and did a Det once for Projection; started off with a 2 week layover (prev-COVID) in a 3rd location in hotels with rentals, then stayed in Hawaii, Guam, Okinawa, Tokyo, Misawa (including extra "waiting for parts" days in Okinawa, Guam and Hawaii
) and included a Remembrance Service at Asan Beach in Guam, complete with a fly-past from a B-52 from Andersen. I also brought home my $800 CAD and a bit more in shopping (once in a lifetime opportunity, right?) and had a decent
amount of change left over when my claim was finalized.
Those all easily outweigh the AIRCRA/"someone at the OSS makes the same salary as me" aspects....
(After writing that, I can't understand why people aren't fighting to get into LRP... 🤷♂️ )