If you go to this link: Medical exams for visitors, students and workers:
https://www.canada.ca/en/immigration-refugees-citizenship/services/application/medical-police/medical-exams/requirements-temporary-residents.html#when It says :
"When to get your medical exam
You can either get your medical exam before or after you apply.
Getting an exam before you submit your application
You have the option of getting an exam before you apply. This is called an upfront medical exam. To get one, contact a panel physician directly.
You can get one if you apply to:
visit (including parent and grandparent super visa)
work
study
Getting an exam after you submit your application
We’ll send you instructions on how to get your medical exam done. You must go for your medical exam within 30 days of receiving these instructions.
If you don’t follow these instructions, we may refuse your application."
Am I missing something here?