I would say FL285 NEG RVSM and FL295 RVSM Approved is not a STD, because the RVSM band applies for 1000 foot protection from FL290, not from FL295, FL285 + 1000 isn't ok unless RVSM approved, unlike FL280 + 1000.
It's about the 'tollerence' applied to the non-RVSMer in this case, it's not about the one approved as such. Ask yourself what sep would you need if the Non-RVSMer was at FL290, or FL300 what minimum would you apply above or below? So I'd be applying those "standards" to any level above FL280.