It also said that full grown bulls were 'only roughly larger than a calf' due to breeding practices at the time. To me, that seems ridiculous. How did the cows pull a plow if they were so small? How did people make clothes with such tiny fleeces?
(My initial comment was wrong brcause I misread ounces and pounds. This first paragraph has been edited.) 2lbs, yes. 2 ounces, no. The article you link is just wrong, but wool yield was lower on average than modern wool yields.
My main source on this is Stephenson, 1988, see citation at the end. Stephenson looked at account rolls from manors, which recorded total number of sheep and total weight of fleece. Some groups of manor-estates had relatively low weights - the large Winchester group had 1.35lb for the years 1209-1454. Others, such as the Holderness estates, a average of 2.42lbs.
However, it's important to keep in mind that fleece type (shortwool vs longwool). While average yields have increased over time, it is not all attributable to simply better nutrition and better farming. Stephenson tracks the long term changes (positive and negative) across the data, and suggests some factors.
M.J. Stephenson, "Wool Yields in the Medieval Economy," The Economic History Review New Series, Vol. 41, No. 3 (Aug., 1988), pp. 368-391