Indeed, all it would need is a short confirmation tone. What's incredible is how many complaints, hacks, and workarounds there are online for something that should be a simple fix on Google's side. I don't think this update really fixes it at all because my speakers are in different rooms from my lights.
This wouldn't be so annoying if they would work on context-aware volume. I typically have my speakers on high volume during the day to listen to music, but don't really appreciate when later that night it blasts "OK, TURNING OFF THE MASTER BEDROOM LIGHT!" - seems like all it would take is having the device respond at approximately the same volume you said "hey Google"