The first I heard that one reason for circumcison was to curb masturbation was here on Zity. Never occurred to me nor do I see it as a practical method to keep a guy from masturbating. Is masturbation percieved to be more pleasurable for an uncircumcised guy?
That is one of the oddities of the whole anti-masturbation aspect of circumcision. The procedure was indeed (partially) touted to curb/stop masturbation (starting with Dr. Tissot, a Swiss physician in the late 18th century), but anyone who'd been cut still played with themselves. So you'd think when they grew up to be head of a household or perhaps a doctor or whatever, they'd compare their own youthful experiences with the given reasons.
But, apparently cognitive dissonance is a very real and much occurring mental phenomenon ...
Here's a link to more about the person who started linking masturbation to circumcision in order to prevent all manner of illnesses and mental disorders.
https://en.wikipedia.org/wiki/Samuel-Auguste_Tissot
He probably drew the same wrong conclusions that researchers did in the late 19th and early 20th century, when they discovered that virtually all prisoners in jails, admitted to masturbating when young. Ergo, they thought, masturbation must therefore be a precursor to criminal behavior and to be prevented at all cost.
Tissot probably found out from treating the mentally ill and those with debilitating diseases, that they had all masturbated when young. Therefore, his conclusion was that such disorders/diseases were caused by masturbation, since they all had masturbating youngsters in common.
And what is even odder from a cognitive point of view, is that all these people, learned doctors and all, considered rubbing a penis with a hand, to be entirely different from rubbing a penis against the vaginal walls of a woman. As if rubbing wasn't rubbing. Did they think that vaginal secretions gave the act some sort of magical infusion of health perhaps?