I confirm, I have the same problem
from krita import *
w = Krita.instance().activeWindow()
v = w.activeView()
c = v.canvas()
c.setZoomLevel(1.0)
print(c.zoomLevel())
Result:
4.166666666666667
And zoom is 100% in UI:
But, if you set your document to 72dpi, then result is:
1.0
Not sure to understand why returned zoom level is dependent of image resolution… 
For me 100% zoom level should return 1.0, whatever image resolution is.
Grum999