My understanding of seating allocations is that someone at Crocky's has decided they want to play Tetris during 4-6 weeks.
They have a list of ticket orders and a seating map. Here we go.
At the beginning (the first rows) it's very easy, first in first served. Inevitably, they quickly get overloaded when too many big 4,5,6 seat blocks. All the seats must be in the same row, very complicated. Must delay to next row. That allows them to fill the previous row with whatever they want. You may get lucky. Or not.
Another strategy is to preferably put the big blocks in the middle and small one on side.
Sometimes last minute there's a guy in the crew who needs 2 great tickets to impress a girl. No problem, they have 4-6 weeks to release the seating map. Two people will disappear from 1st row and ... they will probably spend the rest of life wondering how come they were so quick and got only 15th row...
What I'm saying is for most people it will be first in first served and a few ones may not understand.
Two years ago, the ticket I actually got at one venue was different from the one I was assigned by email.
Not very professional and I'm weighing my words. That's one of the reasons why I can't trust them anymore, especially when I get a poor seat.