You are protected from two type of spam lists in Truecaller and both are limited to only detect the Top spammers therefore numbers with lower spam score will not be flashed on screen like on Android due to limitations on Apples platform.
Here are the two spam lists:
1.) Activate "Top spammers" (block is possible):-
- Tap on the profile picture in the upper left corner
- Tap on 'Settings'
- Tap on 'Top spammers' and toggle it on. A contact named "SPAM" will now be created in your phone book and your screen will flash in red when a number in that list is calling you.
How do I block them? Go to your Phonebook > SPAM > Edit > Choose "Block this caller" in the bottom. Important, you'll NOT know if the person has called or texted. The block function is iOS own.
2.) The CallKit list which you activate in 'Call Blocking & identification' settings (not possible to block):
- Open 'Phone Settings'
- Tap on 'Phone'
- Tap 'Call Blocking & Identification' and toggle on Truecaller. This list cannot be blocked like the "SPAM" contact. We do the best by warning you so you can decide to pick it up or not.
Hope this clarifies a bit more.