The old "40 caliber Glock barrels do have enough chamber support" is one of those things that had some merit many years ago but is extremely dated information.
Sadly it gets repeated by people who don't actually have any personal experience. They simply read something on the internet and repeat it. Usually the information they have read on the internet is not actual first hand information either. It is literally repeated like a parrot over and over by others until it becomes "internet fact".
It is much like the "You must be limp wristing it" phenomenon that has become that catch all response for any semi auto malfunction. People who literally could not describe the cycle of operations of a firearm if their life depends on it will gladly diagnose any issue with a firearm without any real information. If it malfunctions, then "You must be limp wristing it".
Along that same line, any time a .40 caliber Glock is brought up, it must be "poor chamber support". This is in spite of not having any verifiable information. This is the "Limp wristing of the .40 S&W" world. In spite of the fact that Glock changed the chamber dimensions more than 2 DECADES ago.
2nd Generation Glock .40s did have issues, but that was more than 20 years and over 1 MILLION .40 caliber guns ago.
Here are some pics not pulled off the web, but from my bench.
Here is a .40 cal Match grade KKM barrel. You can see the chamber support:
And here is a Gen3 Factory Glock 22 .40 barrel:
And here is a Les Baer .45 Match barrel and its "Chamber support" for comparison:
Confirmation Bias is the tendency to interpret new evidence as confirmation of one's existing beliefs or theories.
Quite often they are wrong.
The punchline is that people repeat the same information and come to conclusions without verifying any facts.