When the warden comes out of the ground, it cannot hear vibrations or detect entities until the animation is complete. This also applies when the warden is digging down.
Linked issues
Comments 3
It is also invulnerable during these animations. You can try punching the warden, but it won't take any damage.
That would be MC-249425 🙂
Seems to be intended.
Code analysis (Mojang mappings, 22w12a):
Warden#shouldListen(...)returnsfalseif the wardenPoseisDIGGINGorEMERGING.