In 1.21.0.20 they now changed the cobweb sound from stone to become unique sound. However the sound event ID for cobweb (breaking and step) uses web instead cobweb, which this inconsistent with item name (Cobweb) and/or the flattening will change from web to cobweb in the future update

Steps to Reproduce:

Type in chat

/playsound break.web @s

This also works with step.web