Rendering of CSS classes on Mobile

Hello everyone.

I have a doubt regarding CSS. I had an issue that has this flow in Mobile: 

I hope it is was clear enough. My doubt is why in some moments a certain type of class is being used, and on other moments different classes are being used.

I noticed this because the [.bottom-bar-wrapper] and [.android .bottom-bar-wrapper] and [.ios .bottom-bar-wrapper] were different. 

Normally we see the app rendered with the "normal" CSS classes and not the .android and .ios classes.

Is it because the mobile classes are kept in cache and when the user needs to login the app just decides to render to what is in cache? 

Thanks in advance.