So we gather 20 patriarchal blessings given by a stake patriarch,
say, in Indiana and another 20 patriarchal blessings given by a
stake patriarch in California. We give 10 patriarchal blessings
from each patriarch to someone to read. Each of these 20 is
identified as having been given either by patriarch A or
patriarch B. Then the remaining 20 patriarchal blessings, with
no indication as to which patriarch gave them, are given to the
subjects. Their task is to decide which patriarch gave which
blessing: patriarch A or patriarch B.

My guess is that there'd be no problem assigning the unmarked
blessings to the correct patriarch. Such a result would suggest
that patriarchal blessings come from the individual patriarch,
rather than from God.

You are right.

This is why the cult admonishes members to keep their patriarchal blessings "private." The reason the Mormons give the members, is that "PB's are too sacred and speshul to share."

Lie upon lie upon lie upon lie upon lie

It would be interesting to see how homogenized and unoriginal they actually are.

Totally