It is meant to be 2 pages as far as I am aware. The airline is well within its rights to deny travel if a passenger does not have the correct documentation that they have been told to accept.
TIMATC, while a great little tool, is, unfortunately out of date some times as the relevant authorities don't always update it. For example it states I can just get a North Korean visa and proof of onward travel and I'll be allowed in...not quite.
VS have perhaps had a lot of passengers denied entry recently for not having a blank page so they are right to be cautious. A denied entry is not cheap for the airline/handling agent and not exactly pleasant for the passenger.
For what it's worth, before my trip to SA in 2011 I was advised to have 2 blank pages. I had several blank pages, so was fine. I was under the impression this was for visa stamps or possibly even a visa sticker I have seen on many passports which have been to SA. Upon arrival my entry stamp from JNB was placed on page 2, below several other entry stamps from various places (border guards seem to love page 2 of my passport) and my exit stamp 2 weeks later was placed on page 26, again, right in between two USA stamps. Why I needed 2 blank pages is beyond me as no sticker was even put in my passport and clearly the two stamps are not together.