I still strongly suspect / expect that the problem with the insurance company is that there is not yet a problem that they cover, so they can't check off a required box on the form. I was told that after they processed my surgery claim, and the surgeon THEN diagnosed the ED at a later date as being a direct result of the surgery, it would be at least possible.
My (big national) insurance does not cover any ed med at all unless the ed is caused by a medical condition that they cover. Just getting old and falling apart is not enough. I asked about pre-surgery coverage, and they said no, not covered, period, for anyone under my company's plan.
And yes, Trimix works out to be more economical, but getting the first one approved was a real challenge. Took several weeks of phone calls and a very dedicated pharmacist.