my limited understanding of the flap popping technique is that it is most valuable in a soft field environment where you are nose high for most of the takeoff roll. In this position you are generating material lift (and hence material induced drag) for much of the takeoff roll. Having more flap out increases the low lift and induced drag (and increases some, but probably not a lot the induced drag). So overall you get a material benefit from no flaps (minimising drag while you accelerate) and then 'suddenly' generating enough lift to get into ground effect clear of the retarding effect of the soft field.
I would have thought it would have a very marginal impact on a nose wheel aircraft rolling down the tarmac with a very low natual AoA.
Just a point on the '70% speed by 50% of the runway' - there are a reasonable number of conditions that can result in not obtaining takeoff speed by the end of the runway from the 70% point. If you are only at 70%, the best you are going to achieve is take off right at the end of the runway.