Is soft proofing less critical for glossy or luster papers as compared to mat papers?
As the others (no doubt more expert in these matters than am I) have said, optimal printing workflow benefits from soft proofing no matter what paper is used. But I sensed in your question a different shade of meaning. My experience is that in general, matte papers require more "tweaking" in soft proofing (especially contrast, shadow control, black point, etc.) than luster or glossy papers. If that's the thrust of your question then a qualified "yes" is appropriate I think. In fact, there are one or two luster/semigloss papers I use that require very little tweaking in soft proofing for most images.
Rand