I was playing a game in the Commander Gauntlet League, and my opponent's creatures had ridiculous stats. I am 99% sure this is a bug of some sort. Attached are images of the match.
Can confirm that Commander's Insignia seems to be giving an anthem effect incorrectly scaling off of how many spells you have cast this game instead of how many times you have cast your commander from the command zone this game.
Probably linked to the bugs mentioned in these threads.
I went and tested the other cards that scale off of the number of times you have cast your commander from the command zone (that don't already have threads), and they seem to function as expected.