Allow me to rephrase the paragraph you quoted:
"...do not assume that every part of the Protoevangelion is true. Written extra-Biblical accounts are not Scripture, nor can they be considered to be an innerant conveyor of Holy Tradition in the way that the Scriptures are . In the case of traditions like our beliefs about the conception, birth, early life, ever-virginity, and falling-asleep of the Theotokos, we feel very confident in the basic accounts, but we don't read into small details of the Church's accounts of these traditions with the confidence that we can with Scripture...."
Hope that helps.
Yes, thank you. That does help.