I find it very interesting that all of the talent on the girls side resides in the same dozen or so clubs at each of the age groups.
A few possible reasons:
1) Generally, coach action is needed for girls to get a look. Not all coaches take the time to get their players noticed.
2) Some clubs and/or teams discourage participation. Once and offer is made and it is declined, rejected, or the player is not let participate, Cal South does not tend to ask again. Commitment to the program matters.
3) In order to be evaluated, you typically must be seen playing against top competition. If your are not in CRL, SCDSL Flight 1, or CSL Premier, getting a look can be very difficult. The ECNL players on this list tend to have been noticed prior to ECNL age.
4) Mergers and affiliations have reduced the number of clubs, and placed many girls under the same club name, but the teams may be different.
5) Calsouth does a fairly poor job updating the players' clubs. I expect 10-20% of the players listed no longer play for the club listed.
When you factor in the above, it ends up not being so surprising, although it is still interesting.