They're just wrong.
I'm working with someone who's performing a major NetBackup migration, where hundreds of client are moving from one master server to another. After way too much looking, we discovered why things weren't working: the customer was using bp.conf files in Oracle's home directory. It was a quick way to solve the multi-homed problem they were having a long time ago.
This is the problem with distributed bp.conf files (and .nsr files in NetWorker). They hide out there in the middle of nowhere (since they can be anywhere), then strike when you least expect them to. Please don't use them. Figure out some other way to solve the problem.
In this case, we needed to put the NB_ORA_CLIENT variable in the Oracle backup script.
Please don't use distributed bp.conf or .nsr files. There's ALWAYS another way to do it.
Of course, you can comment on this entry if you think I'm wrong. 😉