True that not all B's have that jumper. My 393 had one, but I removed it and replaced it with an ACR. That way, both banks are charged when there is a source, but are isolated when there is no charging source. Also, I don't have to remember to turn off the engine battery when at anchor.
I also wired in an override on-off switch in parallel, for emergencies. I can isolate a bad bank with the factory switches, and use the override switch to run everything from the remaining bank. OR, combine both banks if needed.