In my headcanon, there is a reason why fluffies refer to themselves as “fwuffy” by default despite their actual product name being My Fluffy Pony.
The reason is that, as they were always meant to refer to themselves in third-person, those not given custom names needed a default name to refer to themselves as. “Fluffy” was the obvious choice, being not only part of the product’s name, but also already a generic and widely used pet name.
Due to a combination of their premature release and peculiar learning abilities, they eventually came to use “fwuffy” not only to refer to themselves but also to refer to others of their kind.
This also helped give rise to the public’s colloquial referral of them as “fluffies” rather than “fluffy ponies” or “My Fluffy Ponies”.