If block top spammers was not enabled in Truecallers block settings then the reason for this is due to low spam marks, in other words "newly marked as spam". The spammers which are automatically blocked are the Top spammers which only contains spammers with higher spam score.
Numbers between 50-200 spam marks can easily been reached within 48 hours therefore not considered as top spammers and therefore not blocked. Top spammers usually have 1000 - 20000 spam marks.
If you have experienced this please our email@example.com and share your thoughts but also the spam number.