You probably didn't get help because your problem as described defies analysis.

Once the chain is off, the crank is turning on bearings, and there's no logical reason for the drag to be different backward vs forward. Possibly (barely) there's some kind of wear pattern on a seal that may prefer one direction, but I can't see it causing a material difference.

So, your option is to first decide that there is a difference, and it's not just your imagination. Then decide if it's meaningful, and not some minor idiosyncrasy. If it clears those hurdles, tear down and overhaul your BB. If it doesn't clear those hurdles put it out of your mind and ride your bike.