I'd just like to add that this is why adoptive mothers in Quebec do not receive maternity leave, but rather welcome and support leave. They are different benefits that meet different needs. They last for the same amount of time, in the interest of equity for all families. If the situation had been evaluated on the basis of needs, more leave would have been required for adopted children in certain instances, but no one wanted to create a new inequity as a consequence of correcting an existing one. That's why it's the same for everyone.
The different wording came about in response to that line of argument.