seems to me that if measured correctly the seat tube on a "48cm" would be that in spite of the wheels being smaller diameter.
Likewise the fork blades would have to be smaller for a 650C wheel (or a "26" as the seller says) but not the head tube or steerer.
I may be off base thinking this (not the first time) but if I'm not missing something i do think that EROS frame is taller than 48cm