> That’s not really true in traditional HFT because resting orders no matter how slowly placed will take precedence over orders that are new.
No. Not everything is FIFO.
You can be last to place a passive resting/limit order at a price and still be the first to receive a fill at that price. And yes, you had the advantage of seeing all the other passive orders at that price.
Examples: Pro-rata markets (SOFR interest rates, some US treasuries), designated market makers (futures, equities), etc.
Source: I work in HFT.