Just wanted to add that I am seeing the same behavior with a new install of WHS 2011 and Drive Pool 1.3.2.7556.
Outside of the "Pool" tab SB seems to be reporting the correct pool size after adding all 5 of my drives. Inside the Pool tab it is indicating that only 1 drive has been added and that the pool is only the size of that drive. The other 4 drives are showing as "Not In Pool"
After reboot drives are shown correctly as "In Pool"