When the local FlashArray is offline, those paths are down, but because the devices are present from both FlashArray's alternate paths are available.
If your testing results in a PDL when bringing the local FlashArray offline, it doesn't appear that it is in a uniformed configuration.
Can you confirm that paths are available to both FlashArrays? When both FlashArrays are available, the local FlashArray (to your local hosts) should have paths listed as Active (I/O) and the paths to the remote FlashArray (to your local hosts) should have paths listed as Active.
