Your initial instincts were probably correct to begin with. The ending was highly embellished. Read this:
Check out this website for more on the lack of historical accuracy in THE SOUND OF MUSIC:
https://www.archives.gov/publications/prologue/2005/winter/von-trapps.html
I count 12 I haven't seen, most of them fairly recent (21st century) blockbusters. The only two pre-21st century titles on the list I haven't seen are ROCKY HORROR PICTURE SHOW and MRS. DOUBTFIRE.