الصَّدُوقُ emphasizes truth in what a person says; الْأَمِينُ emphasizes safeguarding what belongs to or is entrusted by others. The virtues overlap but are not identical.
1. A shopkeeper reveals a small flaw in cloth: truthfulness.
2. A seller guards goods left for safekeeping and does not use them without permission: trustworthiness.
3. A merchant gives accurate details and delivers what was promised: both virtues.
مَعَ النَّبِيِّينَ وَالصِّدِّيقِينَ وَالشُّهَدَاءِ describes the honor of companionship with these groups, not identical rank for every person.