It automagically gave hex support for ReadArgs /N, too, so yes I consider it a good move.
Also, to specify a hex number you need a identifier before such number, thus I can't possibly see any disadvantages in it either.
Backwards compatibility. If you have a function which takes an input string and splits it into int_number and string_remainder then a input string "0x10Hello" would give
0 x10Hello
in the old AOS style implementation (not accepting hex), but
would give
16 Hello in the new MOS style implementation (accepting hex).
Okay, I would probably (have) to think much harder for an example which makes some more (any) sense, but OTOH how likely do you think it is that a similiar enhancement is ever done for clib/atoi() and why.