Searching for the quote you included led me to the original source.
I wouldn't spend too much time worrying about this particular source, and look at some other sources for more information on acquired lactose intolerance. I think there may be some translation/language issues with this section in this particular source. I believe what the author is trying to convey is not that the intolerance is coming from the increased intake, but that the symptoms of intolerance are coming from a sudden increase in lactose intake following a period of low/no lactose intake, where "sudden" essentially means "faster than lactase induction can occur."
That said, I think this is really more an issue of poor wording in a textbook. The whole section is a bit strangely worded, particularly the part on "flatulence" which this author describes as "characterized by increased intestinal motility, cramps, and irritation" - while these issues may certainly accompany flatulence, this definition of these symptoms characterizing flatulence is not correct, as one can certainly have flatulence with normal intestinal function.