Yes, absolutely. https://www.damiensymonds.net/2010/11/colour-modes-vs-colour-spaces.html
This is exactly right. Have no fear, you're doing the cropping to 11:15 perfectly.
However, please assure me you're not actually saving your master file cropped? 11:15 is only for client files, the master file on your computer must remain whole at all times.
And PLEASE tell me you're not sending 11:15 files to the lab to print? That would be catastrophic. Print files must be cropped to the exact size and resolution they need to be.