differences in rooms

Hi im looking to port some of the rooms from Umbrella CHronicles, and I know these rooms are also used in RE Remaster as well. There are 2 different model files for the same room (very similar but different), and was wondering if anyone knows the difference and the reason why there are 2 model files?

Here are the 2 versions:

r102a:



and r102b:


(the railings are missing from this r102b as I did not load them before taking this screenshot)

Thanks for nay help !Happy Modding!