Re: IS the okuda timeline canon?
Might be the case. They probably hadn't really nailed-down a lot of stuff that early on in the production of TNG. In any case, "class of '78" is the anomalous dating reference in comparison to the other on-screen dating references we get in TNG, and should just be discounted. Especially when we get one of the clearest date references later on that same season in The Neuteral Zone
USS Galileo Galilei, NCC-8888
Starbase 31, Daran V
Prima Inter Pares