ULA includes volume of all pockets, they do call out the vol of the main pack itself. I think the circuit is 2400 cu in, with 2900 including expansion collar. Thats about 40L, 50L with expansion collar. It aint no 70L pack. But, like all packs with external mesh pockets, it carries a lot more than you might expect.
I prefer a lot of things in exterior mesh pockets anyway, so Id just as soon they did specify that in pack size like ULA does. Id rather put tent there, raingear there, water bottles there, stakes, poles, water treatment, hand sanitizer, snacks during day, etc.
For a lot of packs, the WAY you load it will make a big difference. Really best to have it at home and play with it there. If you can go to a store, buy it, bring it home, spend a few hrs with it, and take it back if you dont like it. Same for mailorder.