Form mode label translation is overriding interface translation with same label

I have a custom form mode for user registrations called "Register". The form mode label is translated into French "S'inscrire".
These are exported to config correctly.
The main config file contains the full form mode manager config, and thus also the "label: Register".
The French config file contains, as expected, only the translated label: label: "S'inscrire"

I also have a custom twig file that shows user info, login links, logout links, dashboard links and so on...
It contains this piece of twig code:

<a href="{{ path('user.register') }}" title="{{ "Register"|t }}">{{ "Register"|t }}</a>

The string "Register" is translated via Drupal interface translation to "Créer un compte" in French.

If I deploy my project to live, a config import is done and the translation for the form mode manager label is imported correctly.
But, my custom interface translation for the twig string is overridden with the form mode manager config translation...

I have managed to "fix" my issue by renaming/retranslating the form mode manager label. This is acceptable within this project.
But I did not expect that importing config translations would override interface translations...
Is this expected behaviour?