My understanding (such as it is) is that Fred. Dyer actually used sources other that the ORs, that his work is more (and less) than simply a compilation of data also in ORs. Supposedly he incorporated soldiers' recollections into some of his unit histories. I don't know how else to account for some "actions" he attributes to some units which are NOT in the ORs. Of course there are a lot of plain errors in Dyer also, which ought to be used as one source among many, not as a final authority.
John