If your definition of "two regions touch each other" is something like:
. . "Uh, like, it's when two regions are sort of ... kind of ...
. . um ... y'know ... next to each other ... know wot I mean?"
then we have no basis for any conversation.
If your definition is: "the two regions share at least one common point",
. . then we must agree that all four states "touch each other."