IIRC the Scoville Heat Unit is “equivalent parts per million capsaicin” - so it’s already considerably hotter than pure capsaicin is (there are spicier molecules available).
Anyone have a ref while I paw through my memory slowly?
Edit: here it is, resiniferatoxin https://en.wikipedia.org/wiki/Resiniferatoxin
"Resiniferatoxin has a score of 16 billion Scoville heat units, making pure resiniferatoxin about 500 to 1000 times hotter than pure capsaicin.[...] This stimulation is followed by desensitization and analgesia, in part because the nerve endings die from calcium overload"
"At 16 billion Scoville units, resiniferatoxin is rather toxic and can inflict chemical burns in minute quantities. [...] For rats, LD50 through oral ingestion is 148.1 mg/kg.[13] It causes severe burning pain in sub-microgram (less than 1/1,000,000th of a gram) quantities when ingested orally. "
Obviously he does have an incentive to say that! But when someone says "no, plant chemistry is more complicated than that" I'm normally inclined to believe them!