why do some breed note writers say that there is no award for best opposite sex, we all know that the dog papers and pedigree only reward the top in a breed.
  But breed clubs have awards on offer for best op sex, or is it that when they get best op sex it only counts, as they have twice and crowed about it.

I do not understand the question??? At championship shows the best opposite sex is the dog or bitch that didn't go BOB, as each sex is judged seperately.

At a lot of Open shows the sexes will not be seperated, and here there will be a BOB award, and a BPIB award.  The societies may also award Reserve BOB or even BEst Opposite sex.

At the higer level at a show, you will have Best In show and RBIS, and the same for pups, and some shows (couple of all breed champ shows, as well as breed events) alkso have Best Opposite SEx, which is not necesarily the same as RBIS.

As an example at our breed club show in 2001 my bitch won the CC (so was best of sex).  She competed against the male, who was BOB and BIS.  She then had to compete against the Resrve Best Dog for RBIS, had he beaten her and gone RBIS then she would have been Best Opposite Sex in Show.  As it was she got RBIS and BOSIS.

I'm not sure I've quite understood your question, but whether or not there is an award for BOS depends on the type of show.
:)

The show I help run offers reserve Best of Breed because most of the classes are mixed, however in breeds where there are seperate classes for the different sexes the best bitch and best dog are declared. We also have a contest for the best of the Reserve Best of Breed.

At shows where there are seperate classes for the sexes, Champ and Breed shows usualy, then it is common to have a Best opposite sex.

Think that answeres you question, but I am not at all sure what your question was. :)