No, it doesn't mean one of them is doing it wrong, but it means you are doing it wrong.
+1
I am not sure if the OP is receptive to suggestions, but I ask you to entertain the idea that you will be more efficient if you aim for a higher cadence, 80-90. I know 50 may feel "natural" to you if that is they way you have been doing it all along, but if you try a faster cadence I suspect you will eventually like it and get much more power.