Assuming the trad cleaner was telling the truth, it does seem really weird. It'd be odd to have two different cleaners coming weeks apart, let alone on the same day. If it is all legit, maybe the husband just wants to help out his friend who may have a new business and needs the work. Possibly he's just being nice even though they already have a window cleaner really and don't need the trad guys.
The only thing I have which is remotely similar is that I do a customer's inside windows on an 8 weekly basis. They then have another window cleaner (who I've never actually seen) who does the outside.