plugs
It will all depend on who is charging what, and what flexes are used.
For instance, as a domestic model, the Henry and Hetty use a long 0.75mm lead which is hard-wired to the cleaner. These leads are quite likely to be purchased in bulk by Numatic, with the plugs ready fitted.
Other models use a 1.00mm flex which then terminates into a socket, the likes of which can be disconnected easily by the user. The moulded socker outlet is unique to Numatic and therefore they will have had to strike a deal with a manufacturer who could model that socket, and then have the 13amp in the style of what that manufacturer is offering.