Cleaning the Caravan Interior

Being totally new to caravanning my partner and I have been on internet picking up bits of info.  My partner is now telling me that we cannot use 'normal household' cleaning products to clean the inside of the caravan and we have to buy specific caravan products.  She has spotted a cleaning product for £11 per bottle...fenwicks caravcan cleaner.

It doesn't make sense to me why we cannot use furniture polish, soapy water etc for cleaning the interior.  Any advice on this matter would be helpful.  (I hope my partner remains so concerned about the cleaning of the caravan as the house is normally left to me!!!)