i checked again with v2.5
Even for playlist mixers, v2.5 is shuffling the same way as v3 for when you right click/ List/ Shuffle List ie. just vanilla random.
The difference is that with v2.5, when you have grouping headers, MB forces sorting of the resulting playlist by the grouping header where as in v3, the grouping header does not force the sorting ie. MB just takes what ever order the files are in and applies a grouping header. I actually cant remember if that was an intentional change - i think it was because it gives some more flexibility