Just in case there's any confusion, any of these thoughts are entirely my own speculation. I just can't see how any glitch/setback isn't treated as a major thing when something is being done so cautiously.
And why would the NHL (and other leagues) be working on the complicated logistics of a summer return of the playoffs? Well, the NHL is lousy with executives, logistical staff, lawyers, other permanent staff. They are presumably still being paid. Why not give them something to do even if it's merely an exercise? It's probably great practice identifying all of the variables that have to be addressed for the time when the league actually does start in the future. Plus it's a note of optimism for their customers and helps keep the brand in the news.
A setback would be a significant kick in the pants. Particularly if they try to build a business model around advertising.
I don't think the games themselves are the issue.
It's keeping players and staff from testing positive while they live for months in spaces together. An outbreak within a team causing forfeits? This summer Cup will already have an asterisk around it. Imagine if you win a series by forfeit?
They also will potentially have a Public Relations problem in the USA.
NHL is requiring all players and staff to wear face masks when not on the ice. Down there, a particular party is trying to turn this into a political spectrum fight.
I mean, I hope seeing sports stars wearing masks would be good for their society and they could see the folly in some of the violence that this has sparked.
At the same time, you might alienate elements of your fanbase who are caught up in the politics of it all.
I don't see a lot of good coming from a rush to hand out the Cup this year.