Arami! Thank you SO SO much for this link of the full talk! 45 minutes! Just a few days ago I was searching like crazy hoping there was a full video as I only saw the 5 minute one on youtube where they talk about Shannen so I had given up Thank you so much for this!
I just watched it and so many great moments! I loved that Luke said he was there on set even though he wasn't working that day, and he watched Jennie's performance in the slumber party episode and said she knocked it out of the park!

My take on Luke saying his favorite couple was Brenda/Dylan, I think really was his way to say something nice about Shannen while she was sick, they were clearly worried about her and even feeling slightly guilty about the negative things said about her in the past, so he really wanted to send lots of love to her and say anything that sends love her way. If someone asked him a few years before his favorite couple I'm not sure he would have said that, but who knows.

I'll let the rest of you analyze the rest of what was going on in that interview