Maseches Sofrim 6:5 says that there are 3 places where the word is written as לא but read as לו. This seems to mean that there is a difference in how the word would be pronounced if it were לא as opposed to לו. 


 I am unfamiliar with any tradition which differentiates between a cholem and a cholem vav.  Is there a difference in the pronunciation of these two, or is there some other explanation of the halacha from Maseches Sofrim (perhaps that the intention of the reader should be for לו as opposed to לא)?