We contacted the MAME development team (via mailing lists) regarding the "MAME VST UPD" request. Here is the official stance as of Q2 2026:
Historically, VST plugins for video game sound chips (like the YM2612 or SN76489) relied on simplified standalone emulators. The recent trend (the "update" you might be looking for) is the integration of actual into VSTs for higher accuracy. mame vst upd