There is such testing with the 43x. Negative findings. The Slimline guns all operate off the G 43 RSA and have a limited window of reliability. They are less tolerant of optics and things hanging off the dust cover. This is nothing unique to the 43X. The Gen 3 Glock 22 was notorious for choking with WMLs added.
I’m not aware of any such testing with the G26.
Glock, like all gun companies exist to make money, not guns. If people want it, they will make it.
Despite claims are “perfection” Glock, his head many issues over the years. Failing the DEA drop testing in the early 90s which resulted in the voluntary upgrade program from black internals to the current silver internals.; reliability problems with NYPD’s GEN 2 G19s severe enough that clock set up a machine shop at the NYPD range to modify slides and extractors on thousands of NYPD G19s; and all the issues with Gen 3 G22s and WML.