He probably wants you to be absolutely certain that becoming a monk is what you really want, without any room for alternative options.
Otherwise, you would simply end up wasting precious time without achieving neither the goals of the monastic life nor the goals of the householder life.
Those who in youth have not led the holy life, or have failed to acquire wealth, languish like old cranes in the pond without fish.
Those who in youth have not lead the holy life, or have failed to acquire wealth, lie sighing over the past, like worn out arrows (shot
from) a bow.
... so by such a simile do I speak about this person: he has missed out on
the enjoyments of a householder, yet he does not fulfil the purpose of
I say that person is just like this. They’ve missed out on the
pleasures of the lay life, and haven’t fulfilled the goal of the
If you haven't read it already, the book "Broken Buddha" by Ven. S. Dhammika would help you to avoid romanticizing life in Theravada monasteries, especially in Asia. However, at the same time, you should not let it discourage you, as there are bound to be a mix of good and bad experiences when it comes to monasteries and life in monasteries.