Dear Maintainer(s), the patches have been incorporated in Ubuntu's d-i since their 16.04 release ([1],[2]) and I would hope that thereby they have gotten sufficient test coverage in the meantime. I haven't heard of breakages for other architectures and they have positively fixed the issues for s390. Based on this I'd like to propose that the patches be applied to the respective Debian upstream packages. Thanks for your consideration.
[1] http://changelogs.ubuntu.com/changelogs/pool/main/p/partman-base/partman-base_187ubuntu2/changelog [2] http://changelogs.ubuntu.com/changelogs/pool/main/p/partman-partitioning/partman-partitioning_110ubuntu4/changelog -- Mit freundlichen Grüßen/Kind Regards Viktor Mihajlovski