Thanks for the question.
Clause 14, as written, begins with “Subject to the choice” of a first nation. That's the choice over Canada's drinking water guidelines or provisions found in the applicable province or territory. First nations would inherently have the ability to apply standards based on their choice.
The amendment begins with “The Minister must ensure”, which removes the concept of choice. I would also point to clause 18, which speaks to provisions if no choice is made.
It seems that as written, clause 14 and subsequent clauses that are speaking of waste water allow first nations to apply choice on standards, and then, should a choice not be made by first nations, there are subsequent provisions that invoke co-development with the minister.