What historical analysis? I read the paper and didn't find any parallels between Ati and Ch'an. In fact I thought that his analysis of 'no thought' in Ati was incomplete and misjudged. But what can you expect from an Academic who wrote this paper back in 1985. I also found it strange that he didn't quote from Dzogchen tantras.
In fact if you are sincerely interested in the Ati view and how it might be the same or different to Ch'an, then you have to read the original Ati/Dzogchen tantras.
I'm all in favor of informed debate but I'm not sure how much trust I put in academic papers like the one you linked to.
The Blessed One said:
"What is the All? Simply the eye & forms, ear & sounds, nose & aromas, tongue & flavors, body & tactile sensations, intellect & ideas. This, monks, is called the All. Anyone who would say, 'Repudiating this All, I will describe another,' if questioned on what exactly might be the grounds for his statement, would be unable to explain, and furthermore, would be put to grief. Why? Because it lies beyond range." Sabba Sutta.