I was reading Garcia's ECG book earlier and in discussing rhythms, he said that the presence of P waves tell you that the rhythm in question has some atrial or supraventricular component. Aren't P waves normal? Does he mean the absence of P waves?
P waves don't necessarily mean it's a sinus rhythm. For example, in 3rd degree block you'll have P waves totally dissociated from the ventricular activity.
To your original question, the sentence you quoted is correct. P waves indicate atrial electrical activity. This could mean sinus pacing, or some other ectopic site(s) before the AV junction.