You do, however, typically need to set “low power standby” or whatever in the options somewhere - it’s usually not enabled by default - the default is usually to turn the screen off but leave everything else running. Mine drew about 5W in “normal” standby, and is immeasurably low (from our household inverters - I live off grid) in low power standby. It takes about 10 seconds to boot - no big deal.
I believe the low power mode is required (by UK law, at least) to be enabled by default. It's pointless otherwise as almost nobody will go and enable that mode.