If there were truly a bug, then it wouldn’t go here for the official reporting and tracking; there is a FAQ which explains where bug reports go if you want them officially noticed and tracked.
However, it is best to come here and confirm first, which is what you did, so ++@David-Shaked
In this case, it’s not a bug, at least from the way I understood your description.
When you edit any Notepad++ config file (including the autocompletion files), there is a sequence defined in the user manual (https://npp-user-manual.org/docs/config-files/#editing-configuration-files) as the only reliable sequence to get the changes to take effect. If you follow any other sequence, you might get surprising results, or your changes might get overwritten.