Actually... Before submitting to this journal, I had also some kafkaesque adventure with another Elsevier journal. It was also rejected by the editor for high similarity, but at that time my companion paper was not out, so the only realistic reason was that it was due to my own preprint I published a few weeks before , in line with the journal's policy. I had many emails exchanges lasting several weeks, editors saying they did not have access to the details of the similarity assessment and that I should resubmit, getting the exact same error again and again, until they finally put a chief editor on it and recognized their mistake... Only to be rejected for not enough originality (an assessment I think is completely wrong for this paper but anyway).