that contraption is not needed on any cb750 as all the oil that finds its way into the sump will get sucked back into the oil tank by the scavenger pump and the delivery pump will do the rest
like its already been said its not the case on any old britt bike and they all do it if the oil is not drained from the sump before starting with such a small crank case the surplus oil will be forced out through the engine cases and you will be welcomed by a huge puddle of black oil
i have a BSA a10 650 and if its not used for more than a few weeks it will wet-sump and i have to drain the sump and refill the tank but i still prefer to do this than fit one of them taps to the oil lines and it only takes a few minutes
i have heard so many stories of guys forgetting to turn the taps back on after a long lay-up and bang its too late
keep it simple guys the older we get the more we FORget