The new adventurer status being greatly extended for players was done due to the Novice Network being added to the game - SE tied access to the NN specifically to new adventurer status, so thinking that players would like to make use of this service for as long as possible, the limits of eligibility to be classed as a 'new adventurer' were extended.

Also although you can turn 'off' the sprout icon, that is only temporary, as it resets it back when you log out of the game - it will only disappear for good once the requirements are met (formerly a certain amount of gametime logged/certain level reached, but now it's the completion of the entire ARR/HW storyline up to the final 3.57 story, no doubt due to the addition of the level/story skip items now adding the phenomenon of brand new players at the beginning of SB.).