Yeah, this makes more sense, as them acting as a holding company actually adds risk over self-custody, and there's no way that their software department beats Bitcoin's returns. I don't understand how they could be worth more than their Bitcoin.
Discussion
Some entities can't buy Bitcoin directly but they can buy equities.
The premium also reflects their ability to increase sats per share. A normal company's future projected earnings are incorporated into their stock price.
You're right, owning MSTR adds third party risk over Bitcoin in cold storage. It also adds the potential to increase the fiat denominated return beyond holding straight Bitcoin. It's essentially leveraged Bitcoin with much less risk of liquidation.
I find MSTR very interesting but I wouldn't sell Bitcoin to buy MSTR. To me, it looks like much of the volatility has shifted to these Bitcoin derivatives. I think MSTR will play a big role in consolidating Bitcoin's price & then taking it a level higher. $150k this year is still in play IMO.