That's a wierd way to test the clutch.
When you get on the gas hard, do you smell anything? If the clutch is slipping badly, you'll smell something like hot brakes.
I think a better test for a slipping clutch, is to get on the highway and put the car in 4th gear. Get the rpms close to where you make peak torque (3000-3500ish) and punch it. If the rpms rise quickly then you know the clutch is slipping. If they rise slow and steady as usual, then the clutch is holding. The most load you can put on the engine and the clutch is high higher gears at peak torque. This test will tell you without doubt. The E-brake test seems worthless to me. That only tells you if you have a COMPLETLY worthless clutch, as you will be no where near peak torque or loads.