If you look at the examples for λογάς, it is noteworthy that often you get λογάς with another noun. Usually in nom. pl. So it really does seem to be functioning as an adjective. Hard to read the examples as cases of opposition. My quite unsophisticated guess is that the uses and hence the part of speech of the word hadn't been fully settled. I wonder how many examples of it we have?
Here is another example that is annoying me. OK, here you get a noun. But I don't understand the "of" in the definition? So here they are seemingly making explicit the adjectival! In the previous cases one could argue that they used the adjectival English because it was most convenient for giving the meaning of the Greek noun. But now, that argument is unavailable because they are translating it with an English noun. But why the "of"? Is that to indicate that the PRev.Laws passage is about partners? Perhaps so, but I had never noticed that before.
κοιν-ών , ῶνος, ὁ, Dor., Arc.κοινάν , ᾶνος(q.v.),
A. = κοινωνός, which is much more freq., X.Cyr.7.5.35, 8.1.16, 36, 40; of partners in a tax-farming syndicate, PRev.Laws 10.10, al. (iii B.C.).
κοινων-ός , ὁ, also ἡ,
A. companion, partner, τινος of or in a thing, A.Ag.1037, 1352, Supp.344, Men.Epit.499; “τῆς ἐπιβουλῆς” Antipho 5.68; “ἱερῶν” Pl.Lg. 868e; “τῆς ἀρχῆς” Th.7.63, 8.46; ὁ τοῦ κακοῦ κ. accomplice in . . , S.Tr. 730; “ἀνοσίων αὐτοῖς ἔργων” Pl.Ep.325a; “κ. περὶ νόμων” Pl.Lg.810c; τινι in a thing, E.El.637: c. dat. pers., κ. ἀλλήλοις τῶν τιμῶν with each other, X.Mem.2.6.24.
2. abs., partner, fellow, S.Aj.284, Pl. R.333b, Phdr.239c, etc.; “ὁ σὸς κ., οὐχ ὁ ἐμός” D.18.21; “ἴσοι καὶ κ.” Arist.EN1133b3; κοινωνοὶ λιμένων, of a societas publicanorum which farmed harbour-dues, BCH10.267 (Syme); of joint-owners, PAmh. 2.100 (ii/iii A.D.).
3. familiar spirit, LXX 4 Ki.17.11.
II. as Adj., = κοινός, ξίφος E.IT1173.