Fidelity $100 fee for purchasing a Vanguard mutual fund

Wanted to buy some VCMDX (Vanguard commodity mutual fund) in a Fidelity account. For this trade Fidelity would've added a $100 flat rate fee. Trialed a different Vanguard non-index & was the same, $100. Their chat representative couldn't provide an accurate answer as to why. She sent me to a page where a footnote said some ETF trades were charged $100 but couldn't provide a list of funds or where it applied to mutual funds.

Anyone know where to get a list from Fidelity of all ETFs and mutual funds or families that Fidelity charges a $100 fee to trade into?

Does another company (Schwab) charge or not-charge similar fees?