Not sure how many case manufacturers case about the MFi program (I could be dead wrong) but given that a non-battery case has little need to have that accreditation for many consumers to buy it, why adhere to strict guidelines like this.
Clearly Apple wants to have as much control if they are allowing their branding. Makes sense. Esp since broken screens and bent phones are something the genius desk has to deal with.
I do wonder if in the future, AppleCare will adjust their policy to only be inclusive of accredited cases, etc for claims.