This is not a bug in plymouth; the problem is that with the new initramfs-tools upload, /dev/.initramfs is no longer being transferred correctly from the initramfs to the rootfs, with the result that upstart is no longer able to track the PIDs of services that were started in the initramfs and carried over. In particular, this affects bootchart and plymouth.
initramfs-tools needs to be fixed to restore compatibility with the old /dev/.initramfs directory, and only afterwards should upstart, bootchart, and plymouth have a coordinated migration to use /run in place of /dev/.initramfs.
This is not a bug in plymouth; the problem is that with the new initramfs-tools upload, /dev/.initramfs is no longer being transferred correctly from the initramfs to the rootfs, with the result that upstart is no longer able to track the PIDs of services that were started in the initramfs and carried over. In particular, this affects bootchart and plymouth.
initramfs-tools needs to be fixed to restore compatibility with the old /dev/.initramfs directory, and only afterwards should upstart, bootchart, and plymouth have a coordinated migration to use /run in place of /dev/.initramfs.