AxCrypt 1 and 2 work the same way, as you describe, except that the original file *is* wiped. What you are seeing is probably temporary copies created by the application software itself, which AxCrypt has no control over.
This is why we always recommend to complement AxCrypt with full disk encryption for local device security.
There are other scenarios as well outside of AxCrypt’s control where the plain text may be made recoverable, such as shadow copies in Windows and journaling file systems.
If you can actually show an example where the plain text is directly recoverable after opening and closing a file with AxCrypt, please describe the exact sequence of events. Do be sure that there are no recoverable files *before* starting the test.