I am unsure if you are agreeing with me or disagreeing with me, but if you are smaller than in general 6 feet tall, the ISM seems to be very wide in general. If you also look at the numbers, the PN series has some weird geometry in itself. The PS series seems to be good for triathlon setups but runs wide, hence the zip ties and/or move to other saddles. Compare widths of the narrower split noes alternatives and to ISM saddles and you can clearly see the difference.
Take a read on many sites and they discuss this geometry in great detail. As a rider smaller than 6 feet tall, I have moved towards a narrower split noes and have noticed a huge improvement over my ISM. And I like to think I don’t have fatty legs 