Actually based on the numbers from marketshare.hitslink.com that was linked form the article Safari on the Mac is "more of a monopoly" on IE on Windows.Also, Safari has never had anywhere near a monopoly on Macs. When my mom went to pick up her new Macbook from the Apple Store, there were lots of people there recommending Firefox over Safari. Compare that to Windows where, for the longest time, you needed IE to view the help files.
IE = 63.26%
Safari = 4.36%
Windows = 92.52%
Mac = 5.12%
The article says 0.29% share of the total worldwide market, this all implies that:
Windows users who use IE is 68%
Mac users who use Safari is 79%
This could be due to Mac users, in general, being more loyal, that Safari is a better browser than IE so less Mac users have a reason to switch from the default, or some other combination of reasons.