It took another week - with help from the Plat line and from the general complaints office at KLM AMS - but now I have been told, they will cancel and reimburse my bundle.

Lessons learned:

1. Bundle is technically a challenge (for pax)
2. KLM has minor control over the execution
3. Claims 'we reserve a seat' and 'any flight is available' are not correct - if Y has sufficient availability you might be able to book with the bundle, but only if the technical side runs well and/or if it is a weekday and (I guess) Indian daytime - because then they have agents available who might be able to book for you.
4. For me not worth the hassle for now
5. If I were KLM I would step in to either improve execution right away or pull the bundles off the markets for now....