I'm not sure it's worth the effort to require proof of ID for membership---especially since that gets into data security issues. It's just disc golf tournaments, after all. Perhaps it will become worth the effort at top levels, as more money is involved. A lot is taken on faith.
Yours is a rare and extraordinary circumstance; I'm not sure if it can be equated with any other situations. Nobody's re-classifying their age; though I wonder if someone claimed that the age they initially gave was in error, and requested a change that would benefit them competitively, would the PDGA ask for documentation? The only other reclassification I can think of is pro-to-amateur; it does require submission and approval, but the PDGA has documentation already, in tournament results. Perhaps if a pro claimed that, due to injuries or illness, he or she should be an amateur, the PDGA might require something?
Also, like everything else taken on good faith, a trans-female who initially obtained a membership as a female, might never have to prove anything. The question might never arise.
I hear you. It IS possbily not worth the effort, unless proof of ID is immediately deleted upon verification. Data retention policies and privacy laws would make it troubled one way or another. That is as far as the "making cheating harder" arguments go.
For insurance purposes, it might actually be or become a necessity.
Imagine non-member player X hurting someone with a disc they threw, and this player just walks away, unidentified.
Yes, my situation is remarkable indeed, and I assume that the number of transgender people seeking gender-reclassification may ultimately go from single to double digits. Whether it ever gets to triple digits remains to be seen.
Let it be noted that I am not in this from the "I need to show proof of ID, so others must too".
I had brought up this proof of ID issue before I even learned to accept myself as a transgender woman. It was ultimately triggered by the notion that in Europe many sports require proof of ID when signing up.
FYI: in Finland, any * national association's disc golf member with a players license (which incudes PDGA membership), will have supplied their ID copy.
* A players license is required to compete in Finnish sanctioned events. That leads to the assumption that "all" members have supplied their ID copy, but rogue members do exist.
My passport change however (M to F change, first name change), caused me to look into the proof of ID issue more in depth.
For Pro-Am reclassifications, a simple player profile check is enough (rating low enough, when last cashed (must be 12+ months), already reclassified in most recent 5 years - I have performed dozens of these as PDGA Europe Interim Administrator between 10/16 and 11/18) to perform that, without any positive proof supplied by member being required.
For Pro to Am reclassifications where rating is too high, but other conditions ar met, a written statement and doctor's attest would be asked, if "injury" is used as reason for reclassification. See
https://www.pdga.com/faq/pdga-tour/reclassification