On many keyboards, ^] can be typed with ctrl-5. Also, ctrl-2 is ^@ (NUL), ctrl-3 is ^[ (ESC), ctrl-4 is ^\, ctrl-6 is ^^ and ctrl-7 is ^_, all of which can be hard to type on national layouts. Except for ^@, these correspond to the last digit of the character code in octal: ^[ is 033 etc.
The thing to remember is that it is "on several keyboard layouts" not "on many keyboards". The actual keyboards themselves are completely agnostic as to what the chords mean.
