If your source is basing their statement on California law they are incorrect. Which state are you referring to? I think I recall you saying you are attending law school. Generally speaking burglary is a state statute and so standards of element differ. You invite me as a computer repair person to come into your home and I had the intent prior to entering to take property I have clear, 100% committed burglary...in California. The DA will have to prove when the intent was formed, however. This may not be correct in the state your source is familar, but in California the repair person has commited burglary. Check 459 PC of the California penal code and read the statute. Then you might want me to dig up some case law to show, but if you have access to the law school db you can find it online without me.
http://www.leginfo.ca.gov/calaw.html
I defer to your source's info for THAT particular state, but you know its a mistake to apply your source's standards to all states. Each state sets this standard for state laws. Am I making sense?