Strange firing of ChangeDataHolderEvent.ValueChange when player entry

Hi! I faced with such a surprise. When a player enters to server, ChangeDataHolderEvent.ValueChange is fired, which indicates that the player’s health has risen from 1 to 20 (in the case of a healthy player). Is this some bug or is it the way it should be? This seriously hinders writing a player authorization plugin, does not allow me to cancel this event for unauthorized players. If I cancel such an event, a player will actually receive damage to half heart.