Create a folder (myfolder)
Enter myfolder, create two empty files (myfolder/a, myfolder/b)
Go to ..
View permissions of folder myfolder
Set to read-only
Confirm set recursively
Enter myfolder
myfolder/a does not show a padlock icon; opening permissions view does not show readonly.

However:
ls -l confirms myfolder/a is readonly
restarting thunar shows readonly correctly
chmod'ing externally updates the view in (semi-)realtime correctly.