For those of us who do not speak French yet would like to investigate, can you copy-paste the exact wording of the incorrect text?

Ah, I assume this is the 'visualeditor-dialog-transclusion-no-template-description' message, which is "{{GENDER:$3|Vous avez ajouté}} le modèle « $1 » à cette page. Il n’a pas encore de description, mais il peut y avoir des informations sur la <a $2>page du modèle</a>." in French and "{{GENDER:$3|You are adding}} the \"$1\" template to this page. It doesn't yet have a description, but there might be some information on the <a $2>template's page</a>." in English.

That is indeed incorrect in all languages, not just French, as the message is also displayed when editing an existing template transclusion.

In T87130#984415, @matmarex wrote:

Ah, I assume this is the 'visualeditor-dialog-transclusion-no-template-description' message, which is "{{GENDER:$3|Vous avez ajouté}} le modèle « $1 » à cette page. Il n’a pas encore de description, mais il peut y avoir des informations sur la <a $2>page du modèle</a>." in French and "{{GENDER:$3|You are adding}} the \"$1\" template to this page. It doesn't yet have a description, but there might be some information on the <a $2>template's page</a>." in English.

This text in french is what I see.

By the way, the link in english here is awkward. To be correct, it needs to be "the template's page".

I see that the english message says "You are adding".

The french message says "You have added".

Traduttore, tradittore !

I think that the french message has to be corrected towards the english meaning. I am going to do that.

Change 257270 had a related patch set uploaded (by Bartosz Dziewoński):
Remove incorrect information from 'visualeditor-dialog-transclusion-no-template-description'

https://gerrit.wikimedia.org/r/257270

Change 257270 merged by jenkins-bot:
MWTemplatePage: Re-word the no-description text to reflect being always there

https://gerrit.wikimedia.org/r/257270