True, they are vinyl wraps rather than painted. But the point remains the same - VTEC are taking them out of service for re-livery and (allegedly) cleaning, so they brought in sets in to provide cover.They don't need painting as that was done by East Coast instead they are getting vinyl's (or even if it is paint it is not necessary to paint them as it has just been done). As far as I can tell the re-liveried sets are no cleaner (or dirtier) than any other set or before they were 'cleaned'.
While there may not be a technical need for it, there is a commercial one and it is going to happen.