Why do not enable Nanite Imposter by default

Hi Everyone. I am currently using UE 5.2 precompiled version from epic games launcher. I noticed that the ‘r.Nanite.Builder.Imposters’ cvar did not show up because there is a C++ macro NANITE_IMPOSTERS_SUPPORTED was defined to 0 which means I could not use the imposter functionality when Nanite instances become tiny instances. So why disable Nanite Imposters and how can I use them? Many thanks :smile: !!!