You CAN use it on the iMac. What Apple is talking about there is if for example you made that utility on the Mini under Lion then tried to use it on a 2015 iMac that requires El Capitan, it would not work.
Ok will have to try this when I get home from work tonight. Ok say this finally works and I put Lion on my iMac, can I go to Mavericks or is my only upgrade option El Capitan?