You did spend an hour of time without doing anything (waiting for the park to open), so I consider that wasted time, don't you? You can do a lot at WDW in an hour!
I see this a little differently than you do. The OP was quite clear that there was "little" wasted time, not "no" wasted time. In the case of FOP, waiting 1 hour before park opening does indeed waste less time than arriving at the park at 10am and waiting 3 hours. I do agree with you that when someone posts arriving at opening and then riding "without" waiting, that indeed they did their waiting before park opening and not after, but did indeed wait.
But arriving before opening for a wait does a few things:
1) Per your post, you cannot do a lot at WDW during that hour, because it's not open. Nothing else is moving or being done, so
your not idle for that hour,
everything is idle for that hour. For us who arrive early, this is a bonus, no one is doing anything. When you arrive at 10am and go to wait for a ride, you are idle in line while others are riding, eating, shopping, seeing a show, etc. etc. etc.
2) Your not taking any park time to wait and are extending potential ride time for the day. If a park is open for 12 hours and I wait 1 hour before it opens and am effectively riding my first ride at opening, I get a full 12 hours out of a park. If I arrive 30 minutes after the park opens and wait 1.5 hours to ride my first ride, I now only get 10 hours of potential park time.
3) I can do a lot in my hour of waiting before a park opens. I have no problem carrying in breakfast if we'll be eating it immediately and dropping the weight. So, bananas, yogurt, individually wrapped muffin, and a juice bottle for each of us, trash everything when done. We also put on sunscreen during this time, review the map and any show times, ordering lunch on the
MDE app, taking pics, searching for new FP times, etc. etc. etc.