perf-stat does not work for 1ms time interval
Welcome to Ask Ubuntu, actually it is 10ms in 18.04 and changed afterward (In or before 20.04).
I checked on on source package of Linux kernel 5.4, man page of perf-stat mention 1ms. So you will able to set interval to 1ms if kernel is upgraded to version 5 (like: linux-generic-hwe-18.04).