I think printing it as "OS X 10.10" is just a shorthand for "OS X (10.10)", which is necessary since combining roman numerals and digits (i.e. 'OS X.10') is awk

I think printing it as "OS X 10.10" is just a shorthand for "OS X (10.10)", which is necessary since combining roman numerals and digits (i.e. 'OS X.10') is awkward. You would still say it as "Oh ess ten point ten."