What I do if I want to see the endorsed side of the check?
Talk to your bank. If you only want to see the reverse side on a handful of checks each year, they may for a small fee be able to provide that detail. Their answer may differ if the check is cashed at one of their branches, because those checks are processed differently.
If the number of checks you want the details for is large or the fee is more than you are willing to pay, then make a request for that feature to be added. If you are lucky the option already exists in their software, and they just have to enable an option, or pay for a more expensive license.
If they can't make the change, or won't make the change, and further appeals fail, then you can research other financial institutions that have this feature.