It is not, I just checked now (file does not have "read-only" checked when I look at file properties).
It would also be strange if that was the case since I happened to have a SECOND project which also had the same changes to GLO_Origins, in addition to other files I was testing, such as the reflection dialogue. In this second project the exact SAME issue occurs with GLO_Origins, but not with other files which had changes such as the reflections dialogue. It seems like this is something very specific with the GLO_Origins file and the new hotfix.