It's also pretty easy to vendor in your dependencies so that they don't move between the time you commit and the time your server starts. We also support lock files so you don't _have_ to vendor your deps too. Versioning is up to the server you import from, but typically you'd put version in the URL somewhere (ideally a pinned version).
Security-wise, There are other articles out there that detail this but it's not fundamentally less secure than importing from npm as you're still pulling a JavaScript file from the internet in both cases. The cool thing here with URLs is that it's pretty easy to audit and create an allowlist of known-good and trusted servers to import from in your org.
As for vulnerability reporting & patching; I think we're still lacking a good vulnerability database, that much is true, but fixing deeply integrated deps that have vulnerabilities is pretty easy using import maps really.