I understand the 928 is a derivative from the 920 as something for non-GSM carriers. The fact it has slightly different specifications is going to lead to consumer confusion, but I guess the CDMA carriers petitioned Nokia into making their models somehow "better" than the GSM models.

Personally I'd have preferred it if Nokia had a nomenclature like "Lumia 920 CDMA" or "Lumia 820 for T-Mobile".