Bitcoin spot ETF, like any spot ETF, maintains the exact price as native asset, because the operator transfers each transaction directly to the native market (bitcoin exchange). In the sense that when you buy 1 bitcoin in the form of an ETF, the operator who provides this ETF, at the same time, buys bitcoin for you and store it for you. So if the ETF price were to be below the bitcoin spot price, the operator would have to pay extra to the business.

The only situation where a spot ETF transaction is not directly transferred to the Bitcoin market is when 2 ETF holders exchanged (one sold, the other bought) and it happened below the maximum spread provided by the operator.
because above the maximum spread allowed by the operator, you make transactions not with other users but with the operator.