The definition of micro-price is
S = Pa * Vb / (Va + Vb) + Pb * Va / (Va + Vb)
Pa is the ask price,
Va is the ask volume,
Pb is the bid price, and
Vb is the bid volume.
The typical explanation for micro-price is that a larger quantity of shares on the bid than on the ask indicates greater buying pressure, and therefore the "true" price is closer to the ask than to the bid.
But my confusion is: The bid price should be hit by the aggressive sell orders, so the "true" price should still be closer to bid, opposite to the definition of micro-price.
Could anyone help to explain?