I don't think this is a duplicate bug of #332270. #332270 is about a problem in udev rules while this one is clearly an mdadm packaging problem (packages should *not* silently override files in /etc. Especially if the consequence is that they remove your RAID arrays.)
I was hit by this bug too and both the assessment and the workaround suggested by the OP are the same here as well.
I don't think this is a duplicate bug of #332270. #332270 is about a problem in udev rules while this one is clearly an mdadm packaging problem (packages should *not* silently override files in /etc. Especially if the consequence is that they remove your RAID arrays.)
I was hit by this bug too and both the assessment and the workaround suggested by the OP are the same here as well.