I know everyone on the boards says it is the only way to reconcile
Not true. It is NOT the only way. Many people on here have reconciled without demanding total transparency. It is NOT a requirement and it is not true that you can't have trust without total transparency. It is an individual choice. Don't let other posters put things in your head that could cause you to fail at reconciling. One person may need total transparency and another does not. Don't let the one who needs it convince you that you can't trust without it. You most certainly can and many have. If you don't need it, then move on and work on your relationship.
I can think of 3 right off the top of my head that are still posting here that I have never heard say they had total transparency as a requirement. All three seem to be doing just fine.
If you need it, then it works best to get it when the wayward is coming back and WANTS to reconcile. You can then use it as leverage BEFORE you agree to reconcile. After reconciling it is in my opinion a detriment to the relationship to ask or demand total transparency and causes more strife than it is worth.... The former wayward almost always fights against it once you are already in the middle of reconciling and then tell them you want total transparency....
Pick your battles wisely.. If it's a deal breaker, then don't reconcile without it. If it's not, then move on past it. You can most certainly learn to trust again.