I'd guess that it's a French speaker or hurried translator, who's probably heard the English term "self-identify" and not realised we'd normally use a different translation in English.
Why would there be hurried French translations happening in Canadian government public health communications when French is the second language of the country and everything official is in English and French? I don’t think there’s a huge amount of “not realising” going on tbh.
The only issue with this poster that I see is “pregnant people”. The “self identify” bit means you don’t need medical proof of being pregnant to access the service.
Just because the language is the same, and means the same thing (no doctors note required, we believe you) doesn’t mean the subject matter is connected to other things you can self-identify as.
It simply means no medical proof of pregnancy required.