See below... I only noticed it on a cheaper watch, then joked to my wife that the reason it was cheaper was because they had messed up the numerals, then I looked at an expensive one and was blown away. They all use IIII instead of IV. Is there some history here that anyone can enlighten me on?
http://www.au.cartier.com/en-au/collections/watches/mens-watches.html#view-all
While you are waiting for a specific answer about luxury watches, you may be interested in this thread about Roman numerals and the use of 'IIII' rather than 'IV' from Roman times onward.