clarification on version for backports

[Dan Streetman]

I just sponsored this bug:
https://bugs.launchpad.net/ubuntu/+source/memtest86+/+bug/1998834

as the bug lacked sponsorship for a while, the version provided by the
backporter is 6.10-2, while in lunar, the latest version is 6.10-4. As
I explained in the bug comment, I felt it was ok to sponsor the 6.10-2
version.

My question to the team here is, should we clarify and document this
point? Specifically, will we accept a backport that doesn't use the
latest version in the 'from' release?

My opinion is we should require backporters (i.e. person actually
doing the code/packaging backport change work) to use the latest
version available in the release they are backporting from (from the
-release or -updates pocket; i don't think we should require using
-proposed pocket versions), unless the backporter provides a reason
why they needed to use an older version. However, I think we should
accept backports that are no longer using the latest version, if the
new version(s) appeared after the initial backport request/work.

My thinking on that is that I don't want process delays (e.g. finding
a sponsor, delays in reviewing uploads, etc) to force a backporter to
have to repeat the backport work multiple times before we accept it.