is really omf mandatory on ASM/EXAdata/DATAguard ?

Hi people:

I'm just a sysadmin trying to help my fellow DBA co-worker to find the right documentation about OMF and the relationship with dataguard on exadata@dedicate infrastructure on OCI.

Please, if this question doesn't fit on this forum, can be so kindly and move the thread to the correct one?

So here is my point, Doc ID 1910175.1 clearly states that:

"...General Recommendations

1) All files in ASM should be in OMF (Oracle Managed Files) format. There are several advantages of using OMF, some of which are:

"

We learn it on the hard way; one DB on our exadata had some data on the other format (.dbf on our ASM) on our Exadata . And EXAdata didn't allow the Dataguard until all content was on OMF format.