The circulatory system that page talks about is the hepatic portal vein. That's the one I was talking about. Check out the diagram. The veins go into the liver. That page says that the toxins go to the liver "for detoxification,", but that just really means first pass metabolism of stimulants. In the liver the caffeine turns into paraxanthine, which is equipotent to caffeine except that paraxanthine is further down the metabolism chain (less metabolizing needed to convert it into non-stimulating metabolites, therefore less time and overall stimulation from it).
"The coffee does not go into the systemic circulation, unless the enema procedure is done improperly.”
They say "coffee", but what they mean is that the caffeine doesn't go into general circulation. You're not going to get coffee in your circulation no matter how you take it, unless you're mainlining it. Anyway, as explained, the caffeine from a coffee enema is more dilute and metabolized than what you'd get from drinking coffee, and this is why coffee enemas can be better tolerated.
Now, the fact that coffee is more than caffeine is why coffee enemas work. The palmitic acids in coffee are key. They stimulate glutathione production, and that's what needs help. As you know, I've heard you point out that stress lowers glutathione levels.
Other things that raise glutathione: milk thistle seed, NAC, ALA (e.g., from chia), undenatured whey protein, exercise, antioxidants, methylation.
But maybe coffee enemas do a particularly good job of raising glutathione levels. I don't know. But at least they're not the only way. So if anyone still has difficulty with coffee enemas despite their being less stimulating than drunk coffee, they should look into other methods to support their glutathione production.