I failed to reproduce the issue on Fedora 34 (readline-8.1-2.fc34.i686).

$ ./python -m test test_readline -m test_auto_history_disabled -j40 -F
(...)
0:19:35 load avg: 42.40 [10785] test_readline passed
0:19:35 load avg: 42.40 [10786] test_readline passed
0:19:35 load avg: 42.40 [10787] test_readline passed
^C
Test suite interrupted by signal SIGINT.
10787 tests OK.
Total duration: 19 min 36 sec

$ ./python -m test test_readline -j40 -F
(...)
0:03:30 load avg: 41.07 [1330] test_readline passed
0:03:31 load avg: 41.07 [1331] test_readline passed
^C
1331 tests OK.
Total duration: 3 min 31 sec
Tests result: INTERRUPTED