I do some test on linux all works - changes are detected and os.scandir() works but in Windows not - probably there is not unit test which check if os.scandir() is working on open files for writing.

f.flush() no matter since file can be changed in external Python/Java/C#/C++, ... application - anyone can write logs in Windows. I will explain it in next comment. I just write this code to show only problem.

Result from linux STAT = False so only repeat os.scandir() calls. Modification are detected correctly in Linux but not in Windows.

[wagnecaz@nsdptrms01 ~]$ python3 s03_dir_entry.py
dir_entry.stat() /home/wagnecaz/test.txt 1593085189.1000397 since last change 0.001112222671508789
2020-06-25 13:39:49.101368 1593085189.101368
dir_entry.stat() /home/wagnecaz/test.txt 1593085189.1000397 since last change 1.0028572082519531
2020-06-25 13:39:50.103111 1593085190.103111
dir_entry.stat() /home/wagnecaz/test.txt 1593085190.1020408 since last change 1.0026073455810547
2020-06-25 13:39:51.104881 1593085191.104881
dir_entry.stat() /home/wagnecaz/test.txt 1593085191.104042 since last change 1.0023958683013916
2020-06-25 13:39:52.106793 1593085192.106793
dir_entry.stat() /home/wagnecaz/test.txt 1593085192.106043 since last change 1.0023260116577148
2020-06-25 13:39:53.108582 1593085193.108582
dir_entry.stat() /home/wagnecaz/test.txt 1593085193.1080444 since last change 1.0021436214447021
2020-06-25 13:39:54.110500 1593085194.1105
dir_entry.stat() /home/wagnecaz/test.txt 1593085194.1100454 since last change 1.0013866424560547
2020-06-25 13:39:55.111684 1593085195.111684
dir_entry.stat() /home/wagnecaz/test.txt 1593085195.1110466 since last change 1.0022354125976562
2020-06-25 13:39:56.113542 1593085196.113542
dir_entry.stat() /home/wagnecaz/test.txt 1593085196.1130476 since last change 1.0021603107452393
2020-06-25 13:39:57.115450 1593085197.11545
dir_entry.stat() /home/wagnecaz/test.txt 1593085197.1140487 since last change 1.003014326095581

Change is done every 1s and detected in Linux in Windows it is stalled.
2020-06-25 13:39:58.117287 1593085198.117287
dir_entry.stat() /home/wagnecaz/test.txt 1593085198.11605 since last change 1.002938985824585
2020-06-25 13:39:59.119224 1593085199.119224
dir_entry.stat() /home/wagnecaz/test.txt 1593085199.118051 since last change 1.0027978420257568
2020-06-25 13:40:00.121166 1593085200.121166