I think you mean that DIMMs don't need two identical chips like the old SIMMs did.
And I believe this was only an issue on early Pentium systems because of the design of the CPU (to put it simply, Intel stacked two 486 CPUs together which required the pairs of RAM so both CPUs could make use of it).
Macs only needed the pairs when the memory was to be interleaved, allowing for you to squeeze a little more performance out of the Mac.