Keywords From Mac Don't Merge

I’m not sure I framed the subject well above. Here’s the problem…

If I have two or more documents in Scrivener 3 (S3) that each have their separate keywords, when I merge them in S3 all the keywords appear in the merged document. If I merge those same three documents in iOS and reopen it in S3, only the keyword from the main document appears. This means I lost the other keyword(s).

Not sure if this is a bug or a known issue. Until this changes I must, sadly, stay on the Mac only. If I shouldn’t merge documents in iOS that have keywords from S3 please tell me.

Kindest regards,