I would agree that he showed more finishing instinct on the ground before he was champion, but at the same time as champ he's actively fighting the best dudes every time. I would also note that this complaint really only extends to the last two fights against Royval and Erceg -- both of which are known for being guys with exceptional scramble/get-up games who you have to consolidate position on or else they'll reverse and punish you or get back to the feet and get a rhythm going. If you go back to the Moreno bout, he was winning rounds by actively advancing to dominant positions, hunting Brandon's neck, and landing some nasty GnP. I will point out that even in these last two fights he still does this when he gets the chance, it's just that the opportunities presented to him are fewer and far between and he's just a tad more conservative about biting on them. But just look at Round 1 against Erceg: once he was able to consolidate position on Steve, he pinned him against the side of the Octagon, tried fishing for his neck, and was landing some solid ground strikes.
I will also note that however you feel about Pantoja's ground game, you sure as fuck can't complain about him being boring when he's on the feet. He doesn't take a single backwards step, has the utmost confidence in his chin, and marches his opponent down to throw bombs with every ounce of his heart and soul behind them until his opponent is either hurt or in range for a takedown.