With properly trimmed brass (in a bottleneck case) somewhere in the cannelure land margin will be the seating depth for Sammi spec, providing again the case is trimmed correctly.
A pilll has a cannelure for the sole purpose of loacating and securing the pill against recoil of the weapon so the pill don't retract or extend in the case mouth during violent (full auto fire), something you don't need to be concerned with, unless you hold the proper FFL license, however, it also secures the pills when they are jouncing around in your pocket. No crimp relies on case neck tension which may (or may not be enough) FYI, I crimp ALL my handloads, whatever caliber straight wall and bottleneck.
A cannelure has nothing to do with jacket retention at all. If a pill sheds it's jacket, it's time to scrap them all and get a quality bukket.
Because the cannelure is at the ideal Sammi seat depth, seating for maximum accuracy may or may not be in the cannulure groove but contrary to the previous comment. each and every different weapon/barrel combination likes the seating depth in a different spot, so 'loading to the lands' or close to may not be that best accuracy ticket in every case, in fact, in most cases, it will not hold true.
Lots of infor mation on the net, you have to weigh it all for quality and most is intelaced with personal opinion, which means relatively nothing (opinion wide_.