Probably too late to fix for M6 since it's +1 day. I don't hear you saying this is a blocker, just an annoyance.
This is due to changing from INCLUDE to REQUIRE in feature.xml to conform with Tycho 1.1 requirements (which we had to do to support JDK 9).
We can probably change some of them back to the old way, but this change helped me find all the places where the projects were failing to publish sources, tests, docs, plugins, or features. Or where SDK features included sources from previous builds instead of the locally built ones, due in part to the dangers of the -Pintegration flag. Or where the SDK features were simply wrappers for other features, providing no sources or other useful functionality other than being a single feature instead of 2-3 features... a feature-of-convenience, if you will.
I can explore reverting some or most of these include-to-require changes along with the changes to bump versions when I enable the baseline checks to use Oxygen.3 instead of Neon. As I mentioned on the call on Thurs, I expect we may find lots of IUs which have not been correctly upversioned for the Photon release.
In the meantime, you could instruct your IBM teams to use p2.mirror against a larger set of plugins/features.
Here's a more complete list of IUs from which you could generate a p2.mirror script:
You could also ask them to test more often, since there have been A Great Many CI builds of WTP since October 4, and this problem could have been reported, caught, and fixed more quickly had they reported it to you or me.
cc:'ing wider audience so more are aware.
Cheers,
Nick