You are technically correct. Silicon Valley uses P/E when calculating valuation/revenue, because startups are rarely profitable.
They aren't equivalent in the same way that user growth and revenue growth are not equivalent to profit growth. A misinformed statistic for a misinformed view of how to build a successful business.
Valuation/revenue would be price/sales, or P/S if you will. The P/E is a "forward P/E", with P = "today's price" and E = "someone's expectation of next year's earnings".
Short answer I got it from my bloomberg terminal.
Long answer.
P/E is different from estimated( or forward) P/E. See https://en.wikipedia.org/wiki/Price%E2%80%93earnings_ratio