Precisely. And no, running a node does not involve building your own os. It just involves installing core... It's one program. Then another. The argument of verifying code falls flat. Do you read all the lines of core itself? Very few do. Bitcoin is open source too. The point is not that you have to trust. If you're being pedantic then sure. The point is you're relying on a maintainer to send you updates. You should be the one maintaining (updating) your own node. If you're not, then is it really your node?

To Izzy's point, going from already having a node to spinning up your own is a lot harder than just starting from spinning up your own. It involves basically shutting down everything one by one and replacing it with actual software and not docker containers. Which of course involves closing any open channels you may already have. Lost time, lost sats in unnecessary fees.

Running core and a lightning node from scratch is not hard. If start9 is a 1 out of 10 difficulty, I'd say doing it yourself is like 3 out of 10. It's really easy.