Isn't that just a normal difference in natural bonuses from the weapon? Especially since the rank 3+ sf 2% is placed before the smelting bonuses.

So, after I smelted around a little, I couldn't help but notice that some weapons were actually different from others in terms of the bonus received from smelting, even with all other factors held equal.

Is anyone else finding this kind of error - or just me?

Evidence

Isn't it just different properties that were added from identification like some would probably get a skill force bonus or none at all other than that the smelt process bonus would always be the same for me.

yeah I have the same deal going on atm with my bows on my dex toon.

As stated, this is just the bonus from the weapon itself right after identification, just like how skills can have borders, weapons can have more than one bonus attached.