There is a scene in The Phantom Menace where the members of the Jedi Council tell Qui-Gon their decision about Anakin:
MACE WINDU : He is too old. There is already too much anger in him.
Did Mace Windu actually mean Anakin's biological age?
It is well known that Anakin was 10 years old at the time of The Phantom Menace. Is this age really too late to become a Jedi apprentice? As we now know Obi-Wan was even older (12 years old) when he became an apprentice.
Maybe, it was just an excuse to deny? Or..
Is it possible that he did actually mean something different?