If I understand the terminology correctly, if they were wired normally open, then the setting would need to be active low...since there is always current going through them and they are wired normally closed, active high is the correct setting...
This is where you are misunderstanding the description of Active HI / LOW.
All switches NC in series to one pin is holding the pin HI while in the normal running condition.
If that input pin ever goes LOW, tripped switch or broken wire ...., that will activate the EStop. Hence, Active LOW.
If all switches were connected NO in parallel to one pin, the pin would be LOW while running normally. Making the pin HI would activate the EStop. Hence, Active HI.
NC and Active LOW is best as it accounts for any break in the circuit making it a bit safer.
Hope this helps,
Russ