They should be frustrated with the vendor if an upgrade is being held up by the trivial Upstart to systemd conversion for a dozen lines of code. Supporting both init systems combined is an order of magnitude less work than SysV init, and it allows you to rip out a good bit of darmonization code which tends to have details less portable across Unix variants.
It's far more likely that the real cause is one of the many major dependency updates (6 to 7 is like a half decade jump) and the systemd mention is either an excuse or axe-grinding.
It's far more likely that the real cause is one of the many major dependency updates (6 to 7 is like a half decade jump) and the systemd mention is either an excuse or axe-grinding.