Unorthodox progression of skills?

Alright, so, I have an interesting situation on my hands--I started training on the rings at the beginning of June, and I've made some good progress thus far, I guess.

Anyway, the issue at hand is that in the few months I have been training, I have already solidified a front lever, as well as a valid Iron Cross (at least 2 second hold). However, I can still barely hold an advanced-tuck back lever...and I figured it was odd, as most people got the back lever before the cross.

Any thoughts? Does this happen?

You just need to work the back lever mechanics more and the feel of where to be tight. Basically squeeze your butt.

I know my back and legs are strong enough that I can hold them out straight in the movement; rather, I feel like the strength deficiency comes from my biceps...even though I can hold the cross.

biceps? weird, that's about all i can say.