Raising the angle of attack works with carrier-launched aircraft because the catapult assists the aircraft to a speed equivalent to Vr within the length of the carrier, so the induced drag on the take-off run is irrelevant. Carrier aircraft can therefore have undercarriage arranged so that the aircraft has a positive AoA on the ground, and the pilot does not have to rotate the aircraft at Vr.
Land-based aircraft have to rely on their own power to reach Vr and so any unnecessary drag on the take-off run just increases TODR. Hence land-based aircraft begin have undercarriage arranged so that the aircraft has low (if not zero) AoA during the take-off run, and the pilot has to rotate the aircraft at Vr.
This is one of the reasons that carrier aircraft often have poorer take-off performance when operating from land than their land-based cousins. Also it was one reason that (as you point out) the RN launched the Bucc and Scimitar with their tails tied down - the aircraft was launched at rotation AoA from carriers without having to lengthen the nosewheel leg which would have penalised take-off performance when operating from land.
I'm thus very surprised that the Canadian's found that increasing the length of the nosewheel leg on their F5s improved take-off performance.