Well, the show has been on for a whopping 11 seasons, so if Studio Lambert is crafting up stories, then they must be doing a good job of it to get that many episodes on air.
According to IB Times, however, this isn’t the case: Undercover Boss is legit and so are the conversations that occur between workers and business owners.
Source: https://www.distractify.com/p/is-undercover-boss-real