Think about it: Is it better to have a posted speed limit of 65mph and a real speed limit of 75mph, and you just have to learn from experience where the real limit is? Or is it better to post 75mph and fine any driver as soon as they exceed it?
And this applies to most other laws too - we can't expect everyone to know all the edge cases so some leniency for honest mistakes is needed.
Press freedom is limited in Singapore and that is a significant problem for its democracy. As a tourist this is unlikely to impact you. Otherwise, rule of law is paramount in Singapore.
Surely the entirety of the law is encapsulated in your comment. Certainly you won't get in trouble for carrying something as innocuous as an empty vape cartridge. You won't get fined for crossing the road in the wrong place, absolutely.
Singapore is just an example. Its more invasive big brother can be found just north of it.