[Asterisk-Users] Is extension.conf documentation wrong?

[rossi.tek]

In extension.conf i read this:

;   ! - wildcard, causes the matching process to complete as soon as
;       it can unambiguously determine that no other matches are possible


I tried to define:

exten => _50,1,Dial(...)
exten => _5!,1,Dial(...)

If i dial 50, due to asterisk reordering _5! is exectued but in the
comment above it says ! is matchaed only if unambiguous... so what's
wrong with my test?

Thanks in advance
Mario