Can't see what the problem with that is, seems like fair marketing. It doesn't say all other oven cleaning companies, just some, and they probably have a point.
By the time you've read down to that bit you're probably not taking it all in anyway - there's a lot to read.
Can you identify any jobs you've lost as a result of that bit?
Some people (ex-franchisees) like to knock Ovenu on the forums but I met my local guy a few months ago. Had been with them for a few years, seemed a decent and professional person and told me that they'd not failed on anything he'd been told at the outset. He was very happy with them.
At £50 to clean my filthy oven I'll be happy with him too. Now where's his business card?