Yeah I think that's what it is! He looks about 18 (even though he's 27) whereas Dianne actually looks like the 30 year old she is. And so they just look weird together. Joe needs to get in the gym and try to put some bulk on - he's posted pics before where he looks pretty ripped, but his arms are just so skinny?
It is a salutary lesson that no matter how physically fit you may be at 21, you will gradually lose bulk, if you don't keep in condition by the nature of your job, or going to the gym etc Joe clearly lacks upper body strength of the kind developed by pro dancers, which is why he never really tried any daring lifts with Dianne, but was instead lifted by Johannes and others
Having said that, Joe is probably stronger than it seems, since his previous physical job required a wiry frame. There is a vid of him on tour in Jan/Feb, where he arm wrestles with a couple of pro dancers and holds his own. I accept there is a certain technique to this but he had to have some residual strength,.
What Joe lacks, I think, is the stamina gained through conditioning and a proper diet. It was no real surprise that at the end of a grinding tour in Feb, he dropped Dianne in one of the 02 matinees. I think the tour had caught up with him and it sorted the amateurs from the pros