Are you using an or a flash thumb drive ?
When loading split games through OPL, the loader utilizes specific configurations to ensure the multi-part fragments are read sequentially without lag or errors. usbutil v21 ultimate for ps2 usb mode 2 link
The USB 1.1 bottleneck causes slow loading times in unoptimized games. "USB Mode 2" in USBUtil attempts to optimize how data is read. By splitting files, the system can seek specific chunks, theoretically reducing seek times compared to a large monolithic ISO on a fragmented drive. Are you using an or a flash thumb drive