After all, they had no way to know other people's talent without proper equipment to test it out.
If they recklessly try to transplant their relatives' heart with them, there was a chance of rejection and it was also possible for their ranks to be much lower than how it should be if they had never done such a thing.
It was a stupid move.
And if they started training before transplanting the heart… it would be impossible because the mana contained inside the mana heart would have belonged to the other party. Forcefully transplanting will only kill them.
This method is very dangerous and not very popular in that world for a reason.
The other example, the machinery warrior.
This was actually the training for disabled people.
Because for those who didn't have the talent to become a magician but has talent to become warrior but has some physical defects, they would feel deeply regretful for not having even the chance to start their training paths.
