“Of course that explanation is almost impossible for most of us to verify.”
Copies of the 1840 edition still exist. For over 20 years we have been pointing out that the change comes from the 1840 edition but critics just ignore that fact and portray the 1980 edition as the first time pure was used there. What does that tell you?
It tells me the LDS organization was very lax concerning the accuracy of their printings.