This is correct, albeit not universal.

KDE has a predefined schedule for "release candidates", which includes RC2 later this month. So "RC1" is clearly not going to be the final version. See: https://community.kde.org/Schedules/February_2024_MegaRelease

This is at least somewhat common. In fact, it's the same way the Linux kernel development cycle works. They have 7 release candidates, released on a weekly basis between the beta period and final release. See: https://www.kernel.org/category/releases.html

In the world of proprietary corporate software, I more often see release candidates presented as potentially final; i.e. literal candidates for release. The idea of scheduling multiple RCs in advance doesn't make sense in that context, since each one is intended to be the last (with fingers crossed).

It's kind of splitting hairs, honestly, and I suspect this distinction has more to do with the transparency of open-source projects than anything else. Apple, for example, may indeed have a schedule for multiple macOS RCs right from the start and simply choose not to share that information. They present every "release candidate" as being potentially the final version (and indeed, the final version will be the same build as the final RC), but in practice there's always more than one. Also, Apple is hardly an ideal example to follow, since they've apparently never even heard of semantic version numbering. Major compatibility-breaking changes are often introduced in minor point releases. It's infuriating. But I digress.