Minimum system requirements can be widely off, but they can be widely off in either direction. Often these system requirements do not reflect the absolute minimum that the program can run on, but rather the minimum that technical support will offer support on.
When I was working technical support, we listed our minimum system requirements for Netscape 4.5 as being 32 Megs. Occasionally, someone would call in who managed to install it on half of that. We would normally give a normal level of support for this, but if the normal fixes wouldn't work, we would assume that it was due to the lack of RAM, and we would tell the customer that we couldn't proceed past that point.
Depending on the level of diligence and honesty of the technician, people might get shuffled away quite quickly for a very slight lack of system power. In other words, system requirements often became just another excuse for technicians to dismiss their customers.