> I can't say why that is, but I've seen it on multiple occasions.
Because Ubuntu releases are, well, releases. Early in the release cycle, they sync from Debian, they package their own things, then freeze the versions and release. They don't change versions of most packages in released! releases.
Debian unstable on the other hand, has no concept of a release, so maintainers upload new versions of packages into unstable pretty much all the time (except freeze time).
So what you've seen is actually the norm, not exception.
What you're saying makes sense, except that I would expect 15.10 to always be more current than it is before 2015-10 arrives. In reality, it's often not more current than the released version. If there is a new version of a package in sid, why isn't it in the "bleeding edge" ubuntu next-release? (I'm sure it's a good reason)
In Debian, actually, I am pretty sure there's never really a freeze in unstable as you mention. They make a new stable release from the testing branch some time (a good long while) after the freeze is called, then for a brief period you have only stable and unstable (and oldstable), and later on a new testing branch is created (not yet frozen) with whatever packages from unstable meet the criteria to go into testing.
When testing is not frozen, that means "the package has been in unstable for 2 weeks without any reported bugs" or something like that. When they're getting ready for a new release, they freeze testing, and then the criteria to get your package in for the next release gets more stringent (is it, bugfixes only? security issues only? I'm not sure, but it's probably even stricter than I think.)
> What you're saying makes sense, except that I would expect 15.10 to always be more current than it is before 2015-10 arrives. In reality, it's often not more current than the released version. If there is a new version of a package in sid, why isn't it in the "bleeding edge" ubuntu next-release? (I'm sure it's a good reason)
I'm not closely following Ubuntu development, but they have 6 month release cycles and they do the "sync from sid" early in the cycle, AFAIK first 3 months or so, so you can expect 15.10 to have what was in sid on August-ish. This may further skew when
1. Debian is on freeze. For example, Debian was on freeze starting from November '14, which means practically sid was also on freeze. Debian import freeze date for Ubuntu 15.04 was February [0], so while normally you would expect 15.04 to have latest versions of february; in reality they were latest versions of october. (there are, of course, exceptions). When you consider import freeze of 14.10 was August '14 [1], you can see why 14.10 and 15.04 have very similar versions.
2. Ubuntu is importing from testing for LTS releases, instead of sid. This shouldn't matter in an ideal world, where the difference between testing and unstable is 5-10 days, but sometimes packages got stuck in sid so bad that it may cause a difference in what lands in Ubuntu release.
3. I'm not so sure on that but if I understand correctly, they do a complete import of Debian in the beginning of the release cycle, and then maintainers can do ad-hoc imports for individual packages until the import freeze date, so the packages that land in the release may also be older than what was on sid near the import freeze date.
I guess you'll see much newer packages on 15.10, though, since sid will be full-speed during the 15.10 cycle, so nothing to worry about for now :)
Because Ubuntu releases are, well, releases. Early in the release cycle, they sync from Debian, they package their own things, then freeze the versions and release. They don't change versions of most packages in released! releases.
Debian unstable on the other hand, has no concept of a release, so maintainers upload new versions of packages into unstable pretty much all the time (except freeze time).
So what you've seen is actually the norm, not exception.