I do not dispute that, but they were not primitivists. They emptied cities initially, but were slowly allowing small portions to return (only 50,000 in phnom penh by 1979 which in 1975 had 2 million) to build up their theoretical industrial base (supposed to be complementary to the modernized agricultural utopia)
For a good source on how the regime became so bloody, this book is good
https://www.amazon.com/Pol-Pot-Nightmare-Philip-Short-ebook/dp/B003J48BJQ
The extreme anti modern attitude of many cadres was because modernity was asscoiated with the city, and Khmer Rouge propaganda blamed the entire city for American bombings to rile up its members who suffered extreme losses to airstrikes