Novice to stock market.

As far as I know, based on what I have learned, the market prices of etfs are up and down largely according to the holdings. In this case, does RSI, which is the indication of buy and sell pressure, applies to it?

What I mean is, normally, when the lines are apparoching 80, it indicates there is buy pressure, and at the same time, a price tends to be bullish. But for etfs, buy and sell don’t really make a difference to the price because it’s the market value of the holdings that matters the most.

However, somehow, I can see RSI is correlated to the price of etfs, which I found weird.

If a highly liquid etf has holdings of magnificent seven, and all of them are up 10% the past hour, the RSI for each stock will be higher than 80. However, since the etf’s value is based on the price of each holding, the value of the etf will also go up 10%. In this case, why the RSI of the etf is also up over 80?

The demands drive the stocks’ price high, I can get it; in this case, the high RSI and higher price. But the etf’s supply and demand are not going to drive up the price of etf by 10%, it’s the underlying assets that drive up the price. So why RSI of the etf is perfectly correlated to the price of it?