That is not true; 4A Regional Pairings just a few years ago was Big 9 with SPSL. The results favored the SPSL. (There is no 4A metro league. So that is not possible.)

Quick Count of Current Ranked Wrestlers by Region (4A):

Region 1 (W/W) 28 (NPSL/WESCO)
Region 2 (E/W) 16 (GSL/KINGCO)
Region 3 (W/W) 47 (GSHL/SPSL)
Region 4 (E/E) 49 (Big 9/MCC)

The regions try to balance the number of teams in a region. I do find it strange that this 2 year cycle of leagues in each region was completely unchanged from the previous one.

I will say again, it doesn't matter what side of the mountains a wrestler is on, tough is tough. I don't see one side getting favored over the other.