I don't have a problem with the non-mention of Oz. Aside from the fannish glee it would have produced, I don't think it was dramatically necessary, and it's reasonable to assume that no one -- including Spike -- knew how much success Oz had achieved with controlling his werewolfism.
Angel's "you can learn to control yourself, here's an example -- me" was more immediate and positive than "I knew a werewolf who. Um. Was ok aside from the three nights a month they used to lock him in the library book cage and the few times he escaped, and I think he eventually broke up with his girlfriend and left town over it..."
Though there's no reason to believe that Angel even knows anything at all about Oz post-In the Dark
, aside from possibly his breakup with Willow. We see how well they've been keeping in touch in Disharmony
when Cordy doesn't know Willow's Gay Now. Ditto Wes, who seems not to know even in Orpheus
. And while Willow and Fred were apparently trading recipes, it seems unlikely they'd have chatted about Willow's old werewolf boyfriend when Willow's all about
the Gay Now, and can't be allowed to mention Oz even on her own
Spike, having been among the Scoobies and seen the W/T romance blossom, plus being part of Operation Rescue Oz, probably knows something
about Oz' success with controlling himself -- but at the same time, he knows about Oz' failure
to control himself when it came to the woman he loved, so it's not like there's encouraging stories to tell there. Granted Spike was more into telling the non-encouraging sort in this ep, but his general dire predictions were enough to get his point across, without babbling about Red's ex and how his Tibetan mysticism didn't do him a fuck of a lot of good when he smelled the Gay Now on her. Even if Spike were being particularly benevolent, there wasn't a lot that would seem positive to share about the Oz thing, given Nina's worries about whether she could be around the people she loved.