Disable / Dropping Constraints prior to flashback table are handled differently !?

Hello,

we noticed that disabeling a constraint prior to a flashback (to an scn prior to the disable) leads to an ORA-01466 -  "unable to read data - table definition has changed" whereas if we drop the constraint instead of disable it, the flashback works just fine.

Demo Script:

https://gist.github.com/tbo007/7187fb1d2d74a010f3999170cc015488#file-flashback_and_constraints-sql

1. Why does the described difference exist?
2. How does Oracle determine that the table defibition has changed since a given scn?
3. Is there another way to deal with foreign-key constraints and flashback table?

Thank you in advance.

Best regards