Low float and high FDV isn't a valuation. It's a public announcement that 90% of the supply is still coming, with dates attached.
A token trades at $2 and the data site says market cap: $200 million. One line below, fully diluted valuation: $2 billion. Same token, same second, a ten-times gap. That gap is not an accounting quirk. It's a schedule of dates on which new supply hits the market.
— Educational, not financial advice.