He very clearly tried to persuade Rudeus wrong this time.
- Roxy would have died.
- Paul and one or more of the others would have died in a similar manner without the book guiding them through the dungeon.
- Zenith would have remained encased in crystal, presumably forever because they never would have found the secret stairs without going through the teleporter that Nanahoshi knew about.
- Impregnating the beast girls when they're in heat would have resulted in Rudeus losing the respect of his sister and probably the trust of his wife.
How that cascade of events serves Hitogami, we do not know. But he was pretty insistent that going to help his parents was the "wrong" decision.
But we know the outcome Rudeus chose instead benefitted Rudeus greatly despite the cost.
It's not the trickster voice. It's all the super manipulative dialogue techniques that Hitogami has been doing to Rudeus this entire time.