It's not that it excludes activity, it's just that you don't notice swapping until tear itself is getting parts of itself swapped out and in. This after other unused programs have been swapped out. So, the CPU can't do anything because it's waiting for write to SD to complete so it can free up memory to complete tear's need for more memory. If you try switch to another app, you'll just be waiting for that app to be read back in from SD. Swap on SD/mmc/emmc/etc is very slow due to the nature of flash storage.