There's a difference between relying on something and requiring it, which is also reflected in the difference between the rules preventing something and the rules facilitating something. That people can translate "The kobold shifts 1 square" into other terms, and some people do not find it an excessive burden in TotM play, does not change the fact that the design relies on a grid of squares, or that other people found it a burden.
Similarly, it is demonstrably possible to play D&D with descending AC and THAC0. And it's quite possible to translate those numbers into ascending AC and attack bonuses. But if 6th edition used descending AC and THAC0 throughout, it would be obvious that the designers were detached from the needs and desires of their audience.