This simplifies matters. Su Xiao can hold his own against Maha Zoldyck, and so in Maha's eyes, Su Xiao is qualified to stand as an equal. Their interactions are exchanges, not commands, probing and exploiting one another until they reach mutual consensus.
With this foundation, is it hard to trigger a hidden task? The answer is no. Alternatively, the second method to trigger a hidden task is to fight Maha, reaching a level of strength that earns his acknowledgment without causing him concern.
Being powerful brings benefits from all angles, especially when dealing with an assassin family like the Zoldycks. Don't forget, originally Silva poisoned Su Xiao's food. It was a game of chance, and if Su Xiao confidently consumed that food, it would have been a delightful surprise for Silva.
Negotiating with such a family requires either great strength or very high Charm Attributes. With Su Xiao's 8 Charm Attributes, he only ends up with poisoned food—a 'warm' welcome indeed.
