I have seen good number of photos of Bob and Betty. In most of them, they are going to or coming from New York or England or arriving at a Hollywood event. The only physical contact in any of them is Betty holding Bob's offered arm, pure formality. In this photo from 1935, Betty has placed her hand on Bob's forearm, with a 'This Man is Mine' look. To me, there's no showing of feelings by one for the other, as with most of their photos.
Of course the public appearances of show people is not much solid ground to determine anything real about them. But the photo below shows two people who care for each other. Notice how Bob has reached out to grab Buffy's arm. He's grinning and looking directly at her, not the cameraman. A happy couple. Good for them.
P.S. I copied the 2nd photo from the old Earl of Hollywood blog site. It reminds me how much I miss that blog. There was just so much information. I copied a lot from it for my own files fearing it would be shut down, which it was. Drats.