Why don´t these figures match up?

[JtD]

Neither the Spitfires nor the 109's WEP setting were cleared for 15 minutes, wouldn't it be wiser to do a longer time test on combat/climb settings? Then go on to check if the engines can be run at WEP settings with a duration representative for the limits listed in the handbooks and only then check out what the aircraft will gain from WEP? It's fairly pointless to find that WEP performance is accurate, if one plane can fly it forever, and the other one will lose power after a few seconds.