Under review
That is correct.  The master password is a mathematical element of each generated password, so changing it will cause all your sites' passwords to change.  In essence, the only proof you have that you are you is the fact that you know your master password.  If you don't, all bets are off.  If you forget your Master Password, you'll have to restart.  Usually, this involves resetting the password on all your sites.  For this reason, I recommend at least memorizing your email account's password in addition to your master password.