Direct costs of an aircraft being in the air most certainly do include the hourly-based maintenance (as anyone who owns a Transport CofA plane for more than 50 hours discovers) but I don't think the CAA see it that way, based on their other publications.
I doubt it's ever been tested. PPLs doing straight cost sharing aren't likely to get checked, and people flying on their own business don't need to worry about the definition because there is a way to get the lot back.
There's some interesting stuff for business flyers in Article 130, very convoluted though.
TonyR
I don't think anybody here is looking for loopholes. Just trying to stay legal and insured, in common PPL type usage situations.