I doubt there are many better upsamplers in digital audio than Meridian's. I have no proof, only years of familiarity with Meridian and its abilities.
I recall the comment from Meridian about apodizing that they tried many different filters and the one everyone preferred used the most DSP power.
I don't think anything can be read into this other than the complex "shape" of the preferred filter required the most DSP MIPS. I'm sure that all of the filters that Meridian staff auditioned used a lot of MIPS.