To be honest I thought Piplup and Croagunk did qualify as a reference even though Ash didnt connect the dots himself. Seemed pretty on the nose to have those out of all the Sinnoh Pokemon.That's the thing. He doesn't use reserves after Sinnoh. The rest are either his Kanto members making harmless cameos that don't help in his quest or they're forgotten in history.
Which is Kanto pandering, which is insulting considering Ash felt like he never visited Bell Tower before and how the strange combination of Piplup and Croagunk in Sinnoh didn't jog his memories. From what I get, the writers are willing to use Kanto pandering (minus Ash's Charizard despite a freaking Charizard being the main foe in this saga, ugh) but never recall things between Kanto and this series (we still don't know if Alola will suddenly get the middle finger or not...but it's been over 20 episodes).
Forget about using the trophies in his room as a ray of hope. That ray of hope has suddenly dimmed down into a kitchen's light going out.
At least Ash remembered Ho-oh