RAID weirdness clarification

I set up a non-partitionable RAID1 configuration with two drives (sda and sdb) with primary partitions of type FD using mdadm. The RAID device is /dev/md3. fdisk -l shows that there is an intermediate(?) device /dev/md3p1 which I assume is a virtual representation of a partition on the array. It doesn't show up in /dev but md3 does so I'm guessing that is by design. fdisk and dd show a typical FD superblock on sda and sdb. If I then use pvcreate and set up /dev/md3 to be used with LVM, the superblocks on sda and sdb are wiped out but mdadm and the kernel (cat /proc/mdstat) don't seem to care. Is that normal?