Most any hone will benefit from lapping. If a supplier says it is pre-lapped, I'd check it with a straightedge first anyway. JIC.

Every Swaty I've had received some lapping. They are hard and diamond works well on them. Once flattened, a Swaty will stay that way for a long time.

You could get by with wet/dry paper. In the long run, a plate can be cheaper if you do much lapping at all.