Here is a quote from the MM 530G System User Guide, page 242, Delivery Accuracy section:
Pumps are programmed with the 1.0 unit per hour rate and then measured for delivery accuracy over a period of 24 hours, in a laboratory setting.
• Testing has confirmed that the delivery accuracy for the maximum/minimum
bolus/basal amounts are within the +/-5 percent of the programmed value.
• All normal boluses will be delivered within a maximum of six minutes.
• Displacement (piston) accuracy: +/-2 percent.
So, as far as the pump itself is concerned, the statement in Ponder’s book is definitely not true. Variability due to bubbles, site, etc., could be higher, but how high - who knows.
Regarding his statement about battery, having background in electrical engineering, I can with high degree of certainty state that pump delivery performance can easily be engineered so that accuracy remains the same for any battery charge within battery life limits. So, stay rested, no need to replace your pump battery before the pump tells you to do so! The statement in the book is way off the mark.
Having said all that, I still highly recommend Ponder’s book. Some details are indeed stated somewhat carelessly, but I would not take that as a reason to discount the basic principles, methods and techniques described.