I have a question about the instructions for this jacket. It says 'Then cross your arms behind your back', but to get out of it 'You will now be able to uncross your arms and slip the sleeves over your head'

I'm assuming it means cross the the arms in front of your chest, tie them behind your back. Then after you do the 'secret move' it's easier to slide one sleeve over your head and continue with the moves.

Does anyone use this jacket? am I'm missing something?

I used to keep my arms folded /shoulders back as far back( not hug yourself tightly) as I could without looking phony - so when tied,buckled in back I had a lot of leeway to move arms up and over.

Yes, that's a typo in the Ronjo instructions.