This is a explanation I used to try on debate someone on Yuta vs Kashimo. Makes sense?
Kashimo NEEDS to maintain the hand-sign for HWB or else it WILL crumble.
It’s stated that the best way to counter domain is with another domain because anything else has inferior output and WILL eventually get torn apart. It’s stated that anti domain techniques are only a way to STALL domains because the SUREHIT will eventually tear the technique apart.
Now… there is a way to make it so that anti domains techniques last longer/forever and that’s via MAINTAINING their sign. As we see from Yuki vs Kenjaku as soon as she lets her sign go (the simple domain pose) her SD crumbles rapidly compared to when she was holding the pose. We see the exact same thing in Gojo vs Sukuna, as soon as Gojo lets the pose of SD go the sure-hit of Sukuna’s domain begins to tear it apart.
If someone uses HWB in a domain WITH a surehit, unless they apply hand signs to their HBW it will eventually crumble. The only reason that didn’t happen to Reggie’s HWB is that Megumi’s domain didn’t have a surehit to start tearing at his anti-domain technique. THATS how they work.
This also makes sense narratively with JJK’s whole give something up for something in return. With simple domain you give up mobility to counter domain, with hollow wicker basket you give up arms to counter domain.