Great news!

Reasoning was rather poor. He could have just talked about the power of the system, as well as Nintendo's network lagging behind others.

I should have been more clear. My bad. 

When I say poor reasoning I don't mean its a terrible excuse. I mean to say that he didn't think it through. Even if the device is portable, it does not mean that it HAS to be portable. It may double as both a handheld and a console, but that does not mean you have to use both. There are already some games that are portable only because it uses the touch screen only. In the case of Destiny 2, If they needed the system to work solely as a home console to make it work smoothly, they could certainly talk to Nintendo about making that arrangment. 

With that said there could be complications down the line, mainly because of the vocal Nintendo fanbase that would draw the same conclusion and complain its not portable. Not to say it couldn't work portably, but I imagine it could have problems. 

So I think its certainly a decent excuse, but the reasoning itself is poor to me because it is rather short sighted in my opinion.

Surprise, surprise.

I don't think anyone was expecting it, but well done for being clear about it.

I was expecting it. I think Switch could run it though, but only in docked mode, getting it to run below that probably would be tricky. It doesn't look like the highest end PS4/XB1 game though by any means.

Pretty damn reasonable to be. In fact, the most reasonable answer besides 'Switch too weak'

I don't understand why people are saying the reasoning is poor. The project lead said it's not feasible. I think he probably knows more than pretty much anyone in the world what kind of work it would take to get their game onto the Switch and what kind of experience that game would be on the Switch. It's pretty clear he thinks that's not the kind of experience Bungie deems worthwhile to pursue.

I'm sure nintendo requires all games that run on dock mode to be able to run on portable mode. Kind of their whole message with the console, I could be wrong though. 

I think this reasoning makes total sense. The idea behind the Switch is to be able to play your games on the go or at home. The idea behind Destiny is to play tethered to the internet. Being on the go means you don't always have stable internet. There would absolutely be someone (or many someones) who buys Destiny for Switch and then feels ripped off that they can't play on the subway or in an elevator or what-have-you.