Hi,
yes, this is usual.
If you have a Failed 1TB drive and need a replacement, it can be that HPE is unable to get 1TB Drives, because these drives are no longer available on the market.
In this case, they give you a higher (2TB) drive as a replacement, sometimes they are formatted down to the smaller size.
But don't worry, if the Spare Part# is the same, you can use it.
The Assembly# is an HPE Internal (Factory) Number, only the Spare Part Number on the Handle counts for replacements.
Cali