He is willing to give training another shot. I have a good feeling about it. Istredd's approach may be what he needed, or perhaps Wilhelm was in a position where he finally saw it had to happen. Or everything all at once added up to the choice. Istredd's grateful. The last thing he wants is untrained mages going around burning things. It will make what they're doing here difficult.

Istredd is unaware of that element or that this 'Jack' exists, so he is more than happy to get an agreeable answer. He smiles at his friend, things are always easier when they're on the same page. This night is an example of it. You have a seeing-eye mage to do the same for you, it has to count for something. Istredd doesn't know what seeing-eye actually means, he got the assumption that it meant the angel would do anything for Dean.