Battle Familiar and Find Familiar

Quote from Aidal >>

I feel that's circling back to old ground where the answer is that the Features within the stat block are provided to it by Find Familiar, but to bring up another question I just realized, where is it said that the bullet points within the Find Familiar spell even are Features to begin with? Do other, similar spells list them as such anywhere? Are Features within Features a thing? Skimming various Class Features seems to describe these individual clauses as benefits. The spell Sylune's Viper does the same thing, as does Protection from Evil and Good, though that one doesn't do bolded bullet point

When you summon a familiar in the form of an owl then you have summoned an owl. It has a different creature type, some restrictions on activity, and some extra features granted by the casting of the spell. 

The standard abilities of an owl are not granted by the spell - they are inherent to the statblock of the creature. There is no creature to gain those abilities until the statblock exists, and it is the statblock of an owl already so there is nothing to gain. If you cast the spell to replace the owl with a cat then there is no owl there is a cat. The owl didn't gain cat features, it just is a cat.

So when casting Battle Familiar on that owl it will lose the entire statblock except the hit points, gain temporary hp, and it will keep the telepathy and such granted by the familiar spell, as well as any other features from a Warlock (or other class' features) and from the other familiar-themed feats.