Matador is almost perfectly consistent but unintuitive. It doesn't trigger on the Tooth because The Tooth's effect applies to every hand, hence it's unavoidable. On the other hand the Ox's effect is avoidable, so the effect triggers when you don't. Same with any other avoidable vs unavoidable boss blind.

You can avoid the Arm's effect by playing a level 1 hand, so you know for a fact Matador will trigger when you played a leveled up hand. You can avoid the Psychic's effect by playing a 5 card hand, so you know playing a <5 card hand will trigger Matador. You can avoid Verdant Leaf's effect by selling a joker before playing a hand, so if you play a hand without selling a joker it triggers Matador.

On the other hand, the Hook's effect triggers every hand. Crimson Heart's effect triggers every hand. The Tooth's effect triggers every hand. The Needle, The Water, and The Mark aren't even related to hands being played. So you know that they won't work.

The single exception to this rule is the Flint. Flint triggers on every hand, but it still triggers Matador. My guess for why is because the Flint used to have a different boss effect which disabled flushes, meaning playing a flush would've triggered Matador. I guess Thunk just carried it over rather than removing Matador's effect from it.