No, the EWBS spec was created by Mark Stretton after examining them. He was able to use real aspen, and this is what the weight was based on.
However now that nobody can get hold of it, everybody is using tulip and as a result the arrows are being tapered too soon (right at the head down to the nock) in order to minimise weight.
The actual bobtail taper of the MR arrows is more torpedo shaped, with the taper starting almost halfway down the shaft. You can't do that with tulip, but you can with aspen.