It's not a huge deal. I just saw that you had recently edited it and I hadn't read it. It's also easy to miss when pre-existing New Earth characters make one-off appearances in odd books like that ARGUS one.
I would tend to agree with that; however, I'm working my way through the Forever Evil event and noticed that Bizarro's page is Subject B-0 (Prime Earth). I don't know if the Bizarro designation sets a precedent.
Since he will never (probably?) have a normal name (i.e., Joe Smith), I would lean towards Anomaly and list O.T.A.C. 13 as an alias on his page.
Either way, how should we refer to him in previous issues? Use his page but pipe-link it so that it reads as "Silas Stone Impersonator"?
Your suggestion using pipe-links is my preferred option. I'm not sure what to say about Bizarro; you do have a point but I wouldn't call it setting a precedent. If anything, that page name may need revisiting.