The references were just researchers saying other researchers suggest that it might be active. There is no imperical data or personal experience reporting. No brain scan mri, or chemical or activity analysis.
Metabolic pathways and products hidden behind a pay wall means I can read the outline or summary, but Wiley online or research gate ect. Want me to pay $30 or something to see the entire document. I believe one paper eluded to 13 first pass metabolic processes, so yeah I'm aware there is more than 1.
MAO-a renders nn dmt inactive. MAO-b renders Phenylethylamine inactive. These are metabolic processes. To suggest that first pass metabolism is irrelevant is....insane. sure, you could shoot it up or smoke it to bypass some processes but I wouldn't say that makes it "irrelevant "