Add me to the pile of people who don’t understand how it’s NOT fair as long as both teams have to do it.
It's not the same though. That B2B is the 7th game in 12 days for Tampa. 5th game in 12 days for Dallas. Next game after that is 3in4, 8th and 6th game in 14 days and so on.
Anyone who tracks data for betting purposes knows that this can make a difference. These guys are professional athletes who can play a lot of hockey in spurts and not show a lot of fatigue. It's always the wear and tear from a longer period of time that can ultimately create mental lapses in your game. Assuming all these games in the finals are tough teams are going to have to really lay it all on the line and spend a lot of energy every game, so 7 games in 12 days in the playoffs is really more like 8 games in 12 days in the regular season.
In the regular season it's very common to see teams hit some low energy spots after playing a lot of hockey over a couple weeks like that. See this a lot especially in late February/March when they start pumping the games out after all the breaks are done with, or earlier in the season before christmas break. Doesn't necessarily mean automatic losses, just more mistakes or periods when the legs/mind aren't there.
It's naive to think that just because these teams have the same schedule in the span of a week that they'd be completely on an even playing field for the whole series.
It's not some sort of HUGE advantage for Dallas. At the end of the day it's the stanley cup finals and every player should be able to squeeze everything they have. But it is a potential slight advantage and even winning a couple periods or mistake or two when guys are starting to run on fumes because of it can make a difference.