Care to explain what's so bs about it?
Its your use of ABC Logic. Because Tier wise Pica should be above them, they have no chance.
The problem is, CP-9 has two DF's that are useful in countering Pica's rocks (Blueno and Kalifa). They also have Geppo which makes them not reliant on fighting on the ground only.... countering Pica's greatest advantage over opponents (being able to surround and crush them).
Pica has not shown to have haki. Therefore, he has nothing to suggest he could tank a rankyaku or shigan. His only advantage is large scale earth manipulation which gets countered by Air Door.... Blueno just lets everyone in and they instantly dodge. And Kalifa can make the rock smooth and virtually useless.
It's a matter of ability match ups. For example, you could have someone who has an unstoppable laser eye devil fruit and great Observation haki.... making him capable of hitting anyone at any distance or speed. Yet if he's frail as hell... Nico Robin could clutch him in a one shot.
Pica only has DC/AoE. The problem is his AoE is notably slow, and comes from rocks... which CP-9 can get away from via Blueno/Geppo, or lessen the effectiveness via Kalifa.
I'd still give the win to Pica because its only a matter of time before they wear out from Geppo... and plausibly Blueno's power. And as of now they have no good way to legitimately land a blow on Pica without him moving rock to rock. Unless the Door fruit could isolate him. But I find that event unlikely.
Thus, Pica wins, but it'll take him a while to pull it off.