Rather than let place your equipment as you please, matsuri takes the average of all your equipment for every stat and that is what each ninja gets. This makes the only difference between your ninjas in matsuri which treasured tool you give them. It is an intentional design choice and isn't gonna change. Think of it as a different type of PvP event with its own challenges, sort of like how arena puts everyone at the same level instead what you're actually at.

Ah sorry I forgot that it also counts your 8 gates runes as normal. So stacked treasured tools, and stacked 8 gates runes will result in different bp spreads throughout your lineup. (And also consider that different ninjas have different inherent bps, but I'm assuming you know this and are commenting about how the exact same lineup in the same order has different bps in matsuri and outside it)