Compassion is always coloured by the person being compassionate.
Take, for example, the situation of a peasant levy being horribly maimed, losing both his legs and being in great pain as he lies bleeding on the battlefield; not dead, but certainly suffering.
Is it compassionate to alleviate his pain and save his life, or is it compassionate to swiftly end his life painlessly so he may pass on to his ultimate reward and not be a burden on his family?
The answer is 'it depends' - and it depends on more subtle nuance of the character than a single personality flaw.
As for the mechanical validity of initiating the Gift; if the story involved is fun or the parent's investment is significant enough, I'd have no problem with early initiation of the Gentle Gift.
It doesn't really matter if the child is intended to be a PC later on or not; characters developed through actual saga play from birth shouldn't be bound by balanced virtues/flaws at the point they complete their apprenticeship. Their virtues/flaws should instead be a reflection of what has happened to them through play.
Yes, it means that it is possible for a player to swap to an 'optimised' PC after ~15-20 years of saga play, but they're still going to be 15-20 years younger than the other PCs.