To add more there the recent podcast episodes on Academic Questions Book 2 are causing me to focus for maybe the first time on this kataleptic impression issue. So if I am reading all this correctly the Stoics seem to have made that the centerpiece of their rejection of radical skepticism. If so, then it was definitely going to have been talked about by the Epicureans after Epicurus, and it's easy to see the temptation to say that "some impressions are so clear that the prolepsis and/or the senses themselves can grasp the truth from them without anything else needed."
If that's what happened and that's what led to the adoption of this "fourth criteria" after Epicurus, then I'd lay that as a corruption entering in from the stoics rather than something truly advanced by Epicurus himself or as consistent with Epicurus' views.
In fact I've been thinking about a new thread on articulating better what is meant by 'true opinion."
For example when we talk about defeating the "motion is impossible" argument by demonstrating that you can walk across a room, we probably need to be very clear about what exactly defeats the "motion is impossible" claim.
We're talking as if simply "seeing it" alone is sufficient, and I think the truth is that Epicurus would say that -since the sensations alone contain no opinion" it's still important for us to stress that the mind is processing the sight of the person walking across the room before we can say that the "no motion" paradox is conclusively defeated.