Su Xiao wouldn't tell Luffy that the Netherworld blueprints were with Franky.
Firstly, the CP9 members didn't inform him about the mission of the Netherworld, and secondly, he couldn't explain how he knew the exact whereabouts of the Netherworld blueprints; there were too many points to cover.
So Su Xiao simply didn't mention it, instead subtly guiding the CP9 members to quickly find the Netherworld Design Diagram.
Casting blame on the Straw Hat Pirates is utterly unnecessary, especially with other Contractors helping, it remains uncertain if the blame will stick, and it might backfire.
In the morning at No.1 Dock, Su Xiao proposed directly capturing Iceberg. Kaku disagreed as it didn't align with the plan, but Luffy decisively agreed, showing strong approval.
The final operation in the City of Seven Seas was not planned by Luffy and the others, but rather by their superior, Spandam.
