Everything is engineered. What's the relevance of all these calculations?

Women who, for a variety of reasons, are engineered by medication or NuvaRing and get their period when they want.
It depends on the medicine they take or the NuvaRing they insert.
It could be every 3 weeks, it could be every 4 months. The body obeys the dictates of science. Sometimes they do this, sometimes they do that, as they please.
 
Are all the calculations of menstruation even relevant to them?
It is known that they will receive when they do what they need to do to receive, and neither before nor after.
And even if there are exceptions, it is not related, not even in the area of ​​menstrual calculations prescribed by halakhah.
Just random for medical reasons and all calculations are irrelevant.
So are they exempt from all calculations?