Incorrect. The author of Luke's protoevangelium wants to show that Jesus was Jewish and fully complied with the Law from birth. Luke 2:21-23 shows Jesus following the procedures of Leviticus 12:2-8. Your "interpolation" is required for this. Luke 2:39 should explain this.
In fact the entire protoevangelium is meant to show that Jesus was chosen for his superior righteousness. Luke 2:46 shows how he learned his Judaism through Q&A with the priests and teachers, and 2:52 how he was increasing in wisdom, stature and favor with God. There is another thing we see, in the protoevangelium he has only ῥῆμα (Luke 2:50) which after being filled with the Holy Spirit (Luke 4:1, 4:14) develops into λόγος (4:22 onward).
The passage completely fits the Lukan author's possibly adoptionist theology. And his preference for compliance with the Mosaic Law, not just Noahidic Law. We see examples of this in Acts, making Paul as the foremost teacher of the gentiles, fully follow the Law for himself, such as when Paul circumcising Timothy (Acts 16:3) or shaving his head (Acts 21:24-27), and like Jesus being obedient to his parents Paul is obedient to his superiors, especially James. This is clearly a sectarian view, quite at odds with other views of Jesus and Paul. They clearly show where the author of Luke and Acts falls. While only Noahidic Law need be followed, the key figures in gentile Chrsitianity, Jesus and Paul were personally observant of Mosaic Law from birth.
“’That was excellently observed’, say I, when I read a passage in an author, where his opinion agrees with mine. When we differ, there I pronounce him to be mistaken.” - Jonathan Swift
