That's because the 040 and the 060 have identical cores....in fact the 040 overclocked to 50mhz performs identical as the 060/50
if that was true (identical cores), it would have been called the 050 and not the 060.
taken from:
http://en.wikipedia.org/wiki/Motorola_68000_family"Odd-numbered releases had always been reactions to issues raised within the previous even numbered part; hence, it was generally expected that the 68050 would have reduced the 68040's power consumption...The 68010 was a revised version of the 68000 with minor modifications to the core, and likewise the 68030 was a revised 68020 with some more powerful features, none of them significant enough to classify as a major upgrade to the core."
