CVE does cover "pre-release" software, part of the argument being you can't simply label something as "beta" and escape CVE coverage especially if millions of people are using it (Google's Chrome web browser was a good example of this). For example:
Sure, but Donenfield has specifically declared that CVEs not be issued for "pre-release" Wireguard components[1]:
> Current snapshots are generally versioned "0.0.YYYYMMDD" or "0.0.V", but these should not be considered real releases and they may contain security quirks (which would not be eligible for CVEs, since this is pre-release snapshot software).
Also to reiterate: "which would not be eligible for CVEs, since this is pre-release snapshot software" is not correct. It's usually correct, but not 100%.
https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=prereleases