PDN includes the PCB itself. You need to think about the return currents closely matching. In many cases on 4 layer boards, you are required to have two Vias p

PDN includes the PCB itself. You need to think about the return currents closely matching. In many cases on 4 layer boards, you are required to have two Vias per... Via. (One for the forward current and a second for the reverse current). The PCB also serves as the fastest capacitor. The PCB layers itself form a capacitor measured in hundreds of Picofarads in most cases but more importantly, almost no parasitic inductance or resistance. In many cases, boards are simulated at the Maxwell equation level to understand crosstalk issues. It seems like RP2350 is just fast enough where these effects could be noticed (at the highest clock rate)