When the Create Remainder tool is run on a Multipart parcel, the result is a series of single part parcels instead of a new Multipart parcel with just the overlap area removed. After running Create Remainder, the Merge tool has to be run immediately to combine the parts back together.
This does not make sense as Remaindering a parcel does not ever change whether a Parcel is Multipart or not. The default behavior for the Create Remainder tool should be to Merge all the child parcels from the Create Remainder tool back into one Multipart parcel.
Often, the different parts of a Multipart parcel are widely spread out and it is very difficult to see whether there is a part of the original parcel which needs to be Merged.
Lot A before running Create Remainder tool
Remainder of Lot A after running Create Remainder tool -- the part to the North is a now separate parcel and the Merge tool has to be run to make it a Multipart again.