The constraints would be rule-based. No reason for the administrators to abuse them.
Suppose Presidio, Jeff Davis and Culbertson counties coalese in the early rounds, and aggregate togeather soon after. What then? Unless the number of groups to the West C-JD-P group boundary is an exact power of two, the process will fail [assuming contigious pairings].
This is one reason why it is difficult for computer programs to automatically draw districts. Mapping algorithms start with seed areas, but generally get stuck when an area is cut off that contains a population not equal to a whole number of districts. Programs then have to iterate by unbuilding one or more districts and try to rebuild such that equal population is restored. There are usually several such iterations, and in the process rules that governed the original construction are weakened or bypassed.
