Dr. Squat wrote an article that supports what you'r saying:
Finding The Ideal Training Split | Dr. Squat - Dr. Fred Hatfield
He uses White/red fibres instead of fast/slow in this article, and he's mainly looking at fast gainers vs slow gainers but the theory is the same. People with more fast twitch fibres have a relatively higher 1RM and fatique faster at the same % of 1RM. This doesn't make Frank and Eric wrong. With proper training, the ratio of fast twitch should increase over time and technique would still be a factor.