What is the implication in "Gerald ‘Mac’ MacLean"?

The prefix Mac occurs in many Scottish Surnames: MacNair, MacLeod, MacLean ... an almost endless list. Its original meaning was "son of..". In Scotland it would be unusual to shorten it to 'Mac' because that would lead too easily to confusion with other people.

If such a person is elsewhere in the world, their friends may acknowledge the (real or imagined) Scots origin by calling them 'Mac'. It seems likely that Gerald M MacLean (universities of Oxford and Exeter) may have suffered this from sometimes patronising soubriquet.