Indeed. But they suggest it's 'minimum effort' they are looking for, i.e. cruising in a race, but it's easy to tank a score and still have a high effort.
One way is, from the start pens, instead of pushing 450 watts to stick with the pack, push 250-300 instead. Lose the back wheel and the pack flies off. I'm still exceeding my FTP and HR goes up. I then hold watts at a normal race average for the rest of the race - I've given a normal race effort, but come in last.
Could also race hard for 30 mins, then get 'dropped' by the pack due to a lapse of concentration (we've all done it for real, I've been dropped on descents!), then we tempo to the finish. Result, finish down the results and lower the ZRS.
People will do this and I can't see how it's easy to detect as it's normal in races for riders to get dropped.
Only my personal view, but I think this is a waste of time Zwift trying manage this as it's easily manipulated (I could be proven wrong, and I'll admit so if the anti-tanking actually works). Just accept some people will game the game and concentrate more effort on fixing the initial seedings would be money better spent.