Albeit different Aids, my friend has 1 x 02 and 1 x 03 as she lost a 02 and just bought a 03 on eBay.
Her Aids work fine even tho they are different.
Maybe someone else will understand why.
I’m just going to wait for a very low priced 02 or 03 now. I have one of each now. I’d also like spares, as if a Hearing Aid gets eaten by the dog, I’ll need a spare for the replacement, as the existing Roger X’s are just shells when the receivers are in the HA’s