good catch. however right now it is like a lock+key you use to enter the house.
android has already gottenin the house before you changed the locks. and the session probably lasts for at least a day.

anyway flagging the thread ... lets see what google engineers have to say.

worse is the behavior of lock screen (when pattern is entered incorrectly several times) with passwords changed from web.

ps: not sure ... but one of these might force a signout (clear data for gmail, gtalk, google services, ... from settings > manage apps)