The seventieth is associated in parts of the tradition with a tribe of Israel, and the association points to a structural habit worth naming.
Twelve is the other organising number in this material, and it does not divide seventy-two into the groups the system actually uses. Twelve signs, twelve tribes, twelve months: each of these has been laid over the seventy-two, producing six angels to a sign, six to a tribe, six to a month. Nine is the number the choirs require, producing eight to a choir. Thirty-six is the number the decans require, producing two to a decan. Seventy-two accommodates all of them, which is precisely why it was so useful.
The tribal attributions are the least stable of these. Assignments of tribes to signs, to months, to camp positions and to stones vary considerably between sources, the arrangement of the tribes around the tabernacle in Numbers 2 has been read astrologically for a very long time, and the readings do not agree. Any assignment of a Shem angel to a tribe therefore inherits an unresolved dispute one level up.
This is a recurring feature of the whole apparatus. Correspondence tables look like statements of fact, but many of their columns are downstream of choices that were contested when they were made and remain contested now. The tribe column, the zodiac-to-tribe mapping and the elemental attributions of the tribes are all in that category.
A reader is best served by treating the seventy-two names and their order as the fixed part, because those are what the procedure produces, and everything in the same row as a claim with its own separate history, its own date and, in several cases, its own live disagreement.