I really don't think that's done Winston. You'd clearly see the scarring. They corner a market by only selling males and keeping the females. Spaying is done at a vet clinic and this person is interested in how it might affect a snake for the long term.
For the life of me I can't recall the exact hormones involved in the shed cycle, but I think it's growth hormone and not a sex hormone. Further, both males and females shed equally so I might assume that estrogen is not a major factor (though both test. and est. are produced in both sexes).
Does the vet that did the procedures have access to vin (www.vin.com)? There are many helpfull people on there that always seem to have a relevant resource to whip out and share. Otherwise, you might contact Ken Harkewicz via the www.arav.com website and he might put you in contact with someone that can help.
Your sample size is limited, so it is still quite possible that something unrelated to the spay is going on. I recommend a general health workup if this has not yet been done. This can hopefully be compared to the baseline samples taken when the surgery was first done.
I hope my insight was a little helpfull, I wish I had a direct reference to offer.
Ian