It's a critique of Linux that because it is developed from so many different sources, it tends to suffer inconsistency in how things are done. This criticism is often broadly stated such that it leaves the impression that nothing is ever the same on any Linux system, or even on one's own computer; which, of course, is not correct.
And often times, naturally, we Linux users value that "inconsistency". We like that there is variation, variety, and choice. Sometimes that's one of the top selling points of using Linux at all.