Noel Borthwick [Cakewalk]
I'm not sure what ini file setting specifically you are referring to. There may have been an earlier setting that is now obsolete since I don't see anything configurable related to zero filling presently.
The silent buffer flagging actually relies on our internal zero fill flag that we have had from the 90's! Our old DX SDK had this capability much before VST, so the engine was already silent buffer aware. All we do now is propagate that state to the VST3 plugins so that they can take advantage of it.
Iirc, the setting (in aud.ini?) was called 'Zero Fill Method' (or something like that) and had several options for adding dither-like level variation when buffers were being zero-filled, to avoid putting certain cpu's (Pentium 4?) into a much slower high-precision mode.