Can't change simultaneously modified and creation date/time of files (in some cases)

[misvin]

TC 9.22a doesn't allow to change simultaneously modified and creation date/time in the case if the creation date/time of a file should be equal to its modified date/time.
[AttrPlugin]
Creation Date=tc.creationdate := [=tc.writedate]

Steps to reproduce:
1. Select a file.
2. Click on "Change attributes".
3. Check "Change date/time" and submit a new date/time.
4. Check "Change plugin attributes".
Select Plugin:tc Property:creationdate Value:[=tc.writedate]
5. Click OK.

The modified date/time of the file is changed to a new date/time, but the creation date/time wasn't changed.
Users should again click on "Change attributes", check "Change plugin attributes", click OK. And now the creation date/time is changed and equal to the modified date/time.

Thanks

[ghisler(Author)]

That's not how it works: When you set the creation date to the write date and set a new write date at the same time, then the file will set the old write date as the creation date.

Example:
file.txt write 1.1.2010 creation 1.1.2000
Set write date = 1.1.2019, set creation date = [=tc.writedate]
result:
file.txt write 1.1.2019 creation 1.1.2010

[misvin]

That's not how it works: When you set the creation date to the write date and set a new write date at the same time, then the file will set the old write date as the creation date.

Why the file will set the OLD write date instead of a NEW write date?
If a user checks both "Change date/time" and "Change plugin attributes", then expression creation date = [=tc.writedate] should be equal to a NEW write date.
Thanks