I will disagree with him. He fought Poirier before. He fought him long. The same long karate-type stance with the in and out movement has been a constant. It lets him backstep out of danger and counter hard. The hard counter is what made him dual champ. Or to get full extension to his long left and kicks to land offensively as his opponent circles close to the cage. He did this to Siver, for example.
The compact boxing stance takes those tools away, and puts more weight on his front foot, so not checking kicks has bigger impact. This was a big factor. His own kicks are from closer range, closer to danger, so less free. More blocking is required as he can't use his legs for boxing defense the same way. Conor has never been particularly good at blocking punches. The left isn't as hard, no full extension as the spring comes from his legs.
But the jab gets more pop. Conor has never been a volume jabber, though. With this stance it's a power punch. 3 good ones tops landed. Before he used the lead hand to paw for distance and to disguise the left hammer.
I do agree with Hardy in general that if a plan doesn't work it doesn't mean the idea was incorrect. But here it was. It didn't work. The other style would've been better as Poirier leans forward and plants the legs with his style.
I think the biggest takeaway from this fight to Conor going forward is if he's stubborn enough to still go with this, try to fix the errors that came with it. Or does he go back to a style that made him one best strikers in the UFC. This version is just good at best.