Probably you should read:
"Supported Oracle Products are certified..."
True, ORA-8 is no longer supported. But it being a 32-bit software from the AIX 43 era, it will run on any AIX since then. The 32-bit environment hasn't changed since AIX433.
We still have some ORA-8 databases running on AIX - 43, 51, 52 and 53. We are upgrading to newer versions. Sometimes in a migration path, it may even be necessary to run ORA-8 on an AIX5L platform during your migration.
Make sure you get a patch for Oracle-post-wait kernel extension for AIX5 64-bit kernel, or downsize your AIX kernel to 32-bit, so that your existing PW extension will load into the AIX kernel.
HTH,
p5wizard