In the rules on the game page for Takenoko it says:
I hope this is just an error in the rules, and that it is not implemented this was, at least not in the 2nd edition.
This is not correct and has never been the rule. It was listed as a variant in the 1st edition (Advanced Players Rule), but it is removed from the 2nd edition. This variant made it less attractive to draw plot objectives late in the game, and in the 2nd edition it would be even worse since you can no longer store irrigation channels.If the selected plot or gardener objective is already reflected in the current state of the garden, the objective is placed at the bottom of the deck and a subsequent objective may be selected.
I hope this is just an error in the rules, and that it is not implemented this was, at least not in the 2nd edition.