Might not be coded to make use of it perhaps?
Either way, swap partitions on AmigaOS 4.1FE are not needed these days. Its function is to provide a buffer zone if you don’t have enough physical RAM. As you are using WinUAE, you should be able to allocate more than 1GB of FastRAM. So go with what has been suggested by others. Add Z3 fastRAM to the equation to see if that fixes the issue.