The study is, the article's author is just retarded, as expected.

Participants with processed red meat intake ≥0.25 serving per day, compared with <0.10 serving per day, had a 13% higher risk of dementia (hazard ratio [HR] 1.13; 95% CI 1.08–1.19; plinearity < 0.001) and a 14% higher risk of SCD (relative risk [RR] 1.14; 95% CI 1.04–1.25; plinearity = 0.004). Higher processed red meat intake was associated with accelerated aging in global cognition (1.61 years per 1 serving per day increment [95% CI 0.20–3.03]) and in verbal memory (1.69 years per 1 serving per day increment [95% CI 0.13–3.25], both plinearity = 0.03).
Unprocessed red meat intake of ≥1.00 serving per day, compared with <0.50 serving per day, was associated with a 16% higher risk of SCD (RR 1.16; 95% CI 1.03–1.30; plinearity = 0.04). Replacing 1 serving per day of nuts and legumes for processed red meat was associated with a 19% lower risk of dementia (HR 0.81, 95% CI 0.75–0.86), 1.37 fewer years of cognitive aging (95% CI −2.49 to −0.25), and a 21% lower risk of SCD (RR 0.79, 95% CI 0.68–0.92).

Only the processed meat mentions an outcome for dementia. For "Subjective Cognitive Decline" (self-reported, lol) there was an impact in both groups. However, you'll notice that they quadrupled the test amount to try to get similar risk numbers for SCD across processed and unprocessed. And they didn't measure cognitive ability, they just had them self-report. What would be funny is if red meat made you feel stupid because your cognition is unchanged but you're now aware of a higher potential. Average vegan feels big brained operating at 7/10. Average normal person feels dumb operating at 7/50.