Duration=0 is too slow

I am trying to do instant ON or OFF using power:‘off’ (or on), duration:0 in /STATE PUT URL. It seems the duration is actually 0.4 seconds or longer if above 0.4 value. It did not instantly turn on or off using 0 (or even 0.1) value. It seems to be a bug. How can we ask for this bug fix?

The same for LAN API, looks like the bulb chip is doing some background work and can’t process shutdown immediately. I got Original gen1 and sometimes it takes up to 5 seconds to turnoff.
As a workaround you can set zero brightness, color change requests looks much responsive.
See related thread