I'm aware of the "study" you're referring to. However, he never had his findings published in any journal I could find and he never had his results duplicated by any reputable underwriting lab I could find. It's all well and good to do a bunch of tests, but if your results can't be independently duplicated, verified and validated they're worthless. HOWEVER, if that independent verification and validation has occurred, I'll be the first to praise it ... just show me the light.
I've been casting since 1970 and I've cast conservatively speaking 10,000 boolits per year for that period. A large portion of those have passed through Glock OEM barrels beginning in 1991 with a model 20. But we need to understand, I cast a specific alloy of my design that contains Lead, Tin and Antimony. I don't shoot pure lead except in black powder guns.
I do own after market Glock barrels but they were bought for reasons not associated with cast boolits. For example, my 1991 vintage G20 and 1993 vintage G23 have the original Glock barrels with rather generous "unsupported areas". My G19 barrel and G19 magazines sleeves makes my G26 essentially another G19. There are other reasons.
If someone is uncomfortable with shooting "lead" bullets in Glock OEM barrels, then they should act accordingly.