No the misconception is thinking because it's never shown means he never trains.
Zoro was always a sleeper, there are even gags about it pre TS.
Oda just focuses less on some things post TS, there is no need to show Zoro lifting post TS but he still does. He also probably work on his haki multiple times post TS. And post Wano he porobaly trained his adv CoC, how to control it better just like he trained post Alabasta to be able to cut metal consistently.
Zoro has always been about hard work, it would make no sense for him to stop training and choosing to relax because he thinks he already is the strongest. He always aims to get stronger, that comes with training.
Or else he'd just be betting on getting somehow stronger when fighting black blade Mihawk which make zero sense considering his character.
Post-TS is more than a decade long and there is not a single panel of Zoro training because he doesn't train.
And this is normal because he never lacked in physical training but in Haki and that is exactly what Mihawk did with him for 2 years.
Further physical training achieves nothing and thus he doesn't train anymore.
The only time he "worked on his haki" in post-TS is when he practiced restraining Enma.
There is no training aCoC, it cannot be done. Coating is as simple as CoA coating, if you know how to do it, you cannot make it better.
Yes, he aims to become stronger but every jump in strength is achieved in a battle which further supports that he doesn't train.
Mihawk doesn't train, Shanks doesn't train, Kaido doesn't train, Blackbeard doesn't train. Once you are a top tier, ways of becoming stronger are close to non-existent. There is nothing Zoro can do daily to become stronger, he has reached a wall that he cannot break through with training.