the above posters are right. in the AOA match, you're just ranking programs straight up to start them the next year. thats why most of them are either TRI or CMB (combined progs.). some of the osteo programs that would start PGY2 don't actually participate in the osteo match, they just have their own apps.
the AOA programs in anesth, rads, gen. surg., ortho, etc. are mostly all CMB, or combined internship & residency programs. so when you rank those programs, you're matching PGY1 and beyond.
if you're interested in one of those specialties that start PGY2 (anesth, ophtho, PM&R, Gen. Surg, rads, etc) you can match and secure your PGY2 in the allo match, and then scramble back to get a TRI somewhere.
if you know you're going to go for something like that, and you're sure about it, it makes sense to go ahead and lockup your PGY1, either a TRI or categorial or whatever in the AOA or when you're trying to match allo. The thing is, since the AOA match is so much earlier than the allo match, and open unmatched spots are usually first-come-fist-served, so if you wait to see what happens in allo for PGY2 and beyond, before trying to figure out PGY1, your choices could get limited. but TRI's abound, and so do allo Transitional Internships, so it shouldn't be that big a deal.