I can confirm it and it's bloody hilarious!
"sometimes used in informal conversation to make a joke" - no, it isn't, stop lying.
"potatoes [...] are a limited, underground crop." - that's why Cuzco never rose to power, right? Right? No such thing as the Inca Empire, built upon potatoes, since they're a limited crop. ...or the Irish famine.
I can't... I can't even...
Note: ~a year ago I was testing Gemini and asked it "what's the difference in behaviour between a potato and an orange?", and it "told" me oranges are passive and potatoes are active. That's where the "expression" comes from - I often mock Gemini and LLMs in general with it.
I'll stop doing it, though. Onwards I shall refer to... the potato parable!