Elo factors (aside from constants) just opponents current rating and result, glicko have more moving parts its not just elo + confidence interval. Having two rating (even when elo would be “semi-hidden”) is indeed source of confusion, but just glicko-2 UNTIL IT IS “VALIDATED” is even bigger source of confusion imho.
Glicko and historical data problems are disussed in this thread.
Main point of keeping elo is to give credibility to glicko-2. During elo-period I think I won even games max vs 3 stones stronger and lost max vs 3 stones weaker, while during shorter glicko-period I won vs 5 stones stronger and lost vs 4 stones weaker. Might be coincidence, mighte be glicko-2 shenanigans - this is main reason why I think its good to let elo ratings “validate” glicko-2 ratings.