I dont think this online issue is the key issue for no Switch version but it probably brings up a lot of questions they need to answer.

If ppl use their switch for different games in docked and portabe mode, than constant engagement with their game is lost for something that requires consistent, strong and stable online connection. And they need that constant engagement for an online game that emphasises group play and the released of major paid expansions going forward.

At least that is probably how they see it, so it comes down to whether the community is big enough to remain consistent through the years the game remains active. If they dont think so then it is not worth the cost or efforts to port. Because these costs are also going to move forward with constant updating of the game and the paid DLC to further the games growth and scope.  

Additionally, they have zero idea how the paid online service will actually affect users going forward. i am sure lots of users will pay Nintendo for online, but many might not, and right now they may be unconvinced that the demographic will be heavy into online payments.

So tldr, online-only is just a simple excuse for what is probably a lot of different factors, relating to online, that they need to consider. Budgeting is super important for any project, and there might just be too many unknowns for them to pull the trigger on the effort needed to port and maintain the game.

Yes. Yes, it is.

Hm. Too bad Ubisoft doesn't have the same philosophy as Bungie.

Wrong.  The PS3 and 360 perform at less than 250 GLFOPs (~230 and 240 respectively).  The Switch outputs at about ~400 in the dock and 200 in handheld.  However, real world performance is above PS3 and 360 in both cases due to the additional RAM and other superior tech both hardware and software wise (and also due to he Switch screen being 720p and its smaller size allowing for more variation in resolution and image quality solutions).  In real world performance output, the Switch is closer to the middle between Xbox 360 and Xbox One in the dock again due to the tech.