Why does the 20.04 LTS upgrade say "Do not install it"? [duplicate]

Question

I followed the instructions to upgrade from Ubuntu 19.10 to the final release of 20.04 LTS—

1. Ensure that you have all updates installed.
2. Set "Notify me of a new Ubuntu version" to "For any new version".
3. Run update-manager -c -d.

—and was greeted by this message:

This release is still in development. Do not install it on production machines.

Why does it say this? What would happen if I continue anyway? I double-checked the instructions and there's no indication of how to handle this. I'm not sure if I should:

• ignore the warning and continue with the upgrade,
• take some action to resolve a problem on my end, or
• wait for a problem to be resolved externally.

Details

• The message seems to be coming from this file. There's an analogous one with the messaging I'd expect. Maybe something is just showing me the wrong one?
• This answer (and later DEBUG_UPDATE_MANAGER=1) led me to the release and development release manifests, which link correspondingly to the two message variants. The release manifest doesn't include 20.04 LTS, which might help explain this question.
• That the upgrade instructions specify -d suggests that 20.04 LTS is indeed expected to be a development release. Perhaps I'm mistaken about what it means to be a final release (it's a type of development release?), or the project is simply running behind schedule?
• I asked about this in #ubuntu. A member of the Ubuntu Security Team confirmed that the omission from the release manifest is deliberate, to be changed "when 20.04 is a bit more stable and better tested". This is consistent with the hypothesis that 20.04 LTS is actually a development release, but contradicts the release schedule and announcement.
• The mailing list announcement says:

  Users of Ubuntu 19.10 will be offered an automatic upgrade to 20.04 LTS via Update Manager shortly.

• This answer recounts precedent for delaying the update of the release manifest for a few days after the official release, and warns that bypassing the delay with -d constitutes an acceptance of risk as a tester.