Tony, I don't know how Kubota decided which tractors to put that on and which ones to not. My '95 B7100 had it, but my '99 B2710 does not. It seems if you pour fuel in fast enough to completely cover the screen, that blocks air from exiting and you have a mess, but you can actually pour it in very fast, so long as you don't cover the entire screen; e.g., using a funnel to direct the flow to only part of the screen.
Bird