Do Investment funds buy the coins before they launch an ETF?

Recently, BlackRock registered 'iShares Ethereum Trust' and some voice the opinion that this caused a surge in the price for ETH. Now, if I'm an investment fund, wouldn't I want to buy the ETH before that, to immediately profit from the induced surge in price? In doing so, I could create my investment vehicle at a reduced cost. I guess from a business perspective, this would be the sensible thing to do. But there might be legal considerations and requirements to be taken into account: I would basically cause a self fulfilling prophecy. I buy, announce my ETF, which the market considers as a positive sign, as it attracts new investors and therefore and upwards pressure as well as a higher liquidity. I see the potential to consider this as insider trading or even market manipulation, since the fund knows in advance that it's announcement is going to shift the price and therefore can immediately profit from that. Is the fund therefore obliged to buy after its announcement?

Does anyone have some insights, how this is actually handled?