I am sure it does not mean anything... or that the pool does not work the same...
but I noticed something odd... I rebooted my miner a couple of hours ago and I just happened to walk by and notice the monitor showed best share value of 0
I switched to another pool and within a few seconds I had a number larger than zero populate into the field..
probably not relevant to anything, just an observation.
That's bitmains firmware and bitmains cgminer fork.
It's done that for a long time ... it has no effect on finding shares, just a bug somewhere in their code when recording the best share.