That is not correct. These come from different inventories, and the inventory for SWU/miles is available before that for stickers. In that sense, there is a better chance. Within the 100-hour window, though, it depends upon which inventory is available first.
Cheers.
Guess I could be wrong but IME I have switched to an eVIP or miles+copay on a few occasions when I had to purchase a last minute ticket to improve my odds. Most recently I flew SBA-LAX-JFK and my LAX-JFK complimentary UG cleared immediately when I booked it (~48hrs out) and my return JFK-LAX wasn't clearing. I was 4th on the upgrade list at the airport behind 3 EXP's and I asked the GA if I could burn a eVIP and it moved me to 1st on the list and it cleared 15 mins later.
I was under the impression that on a 3-class plane, C will open before R and on a 2-class plane, A will open before X. Not necessarily true?