It's true, PLs already give an advantage as far as experimenting things. But here, we're talking about giving twice as much opportunities to experiment with the new GE over a few weeks.
We can debate the potential benefits of PLs in normal circumstances, but that's very different. You can hardly compare having a 4th game each week to experiment with tactics, to having double the amout of heads-up time for a new GE.
And what good really is a boxscore if you don't have the players' skills?
I can understand if you need more time with the GE before it goes live, but everybody should be allowed in to the sneak preview.
"Air is beautiful, yet you cannot see it. It's soft, yet you cannot touch it. Air is a little like my brain." - Jean-Claude Van Damme