This is a bit rough since the BP comes from SRM/SCM and there are like no wiki docs on it compared to common module.
The BP role you use play a huge part here. I just tested for you, using FLCU01 Customer. It exist in KNA1. You must be using a different role, probably FLCU00. The same thing applies on the purchasing side, only the correct role will apply the data on the correct table.
If you're an MM guy reading this, remember when we get to select Purchasing, Company Code, data? Well, now its defined by role.