No, I don't think they did that in the windblown study, which I also discounted since it would stand to reason that any trees blown over would be selected for "no taproot" by the wind. But Kolesnikov dug them out, and recently some work has been done using ground penetrating radar ( https://academic.oup.com/treephys/article/19/2/125/1651017
A ground-penetrating radar (GPR) technique was used to study the three-dimensional distribution of root systems of large (DBH = 14 to 35 cm) oak trees (Quercus petraea (Mattusch.) Liebl.) in relatively dry, luvisoil on loamy deluvium and weathered granodiorite. Coarse root density was 6.5 m m−2 of stand area and 3.3 m m−3 of soil volume. Maximum rooting depth of the experimental oaks was 2 m, and the root ground plan was significantly larger (about 1.5 times) than the crown ground plan."
Oaks are supposed to be a taprooted species, but if there were any on these, they only penetrated two meters or less.
Root Distribution of Some Native Trees and Understory Plants Growing on Three Sites Within Ponderosa Pine Watersheds in Colorado
) includes root diagrams from trees in the field. Prominent taproots are absent except in one case, where its depth couldn't be determined because it penetrated a crevice.
I've dug out my share of stumps by hand and never had to deal with any big taproots. It may be that trees shed them as they get larger so they have enough play to shift with the wind instead of just breaking off like they would if the trunk continued straight down. What's good for a small tree may not be good for a big one.
No doubt some trees have strong taproots, but they don't appear to be preferable or even necessary. As for the utility of planting fruit trees from seed, it's a most worthwhile endeavor and if the fruit does happen to turn out nasty, those trees can easily be topworked with something more desirable (or the fruit could be fed to hogs, or turned into hooch and/or vinegar!).