sof.

Oni nie produkują sof.

That of course makes the sentence more vague, but yes, we accept it here.

It is. The thing is, that some grammatical genders have Accusative identical to Nominative. I think it's rather helpful. Those are:

neuter singular (To jest dziecko. Widzę dziecko.)

not masculine-personal plural (like here) (To są sofy. Oni produkują sofy.)

masculine singular inanimate (To jest stół. Lubię ten stół.)

We try to accept 'manufacture' in all the sentence that need it, and it's accepted here.