I rewatched the stage as well, and regardless of when Sevilla started working he and Paredes helped a lot. And Evenepoel working for miles and miles is a bit of an exaggeration as he had more than Serry with him helping when he first started working according to you. Let's leave it at that.
Starting +/-38k from the finish, Evenepoel is working together with Serry. Van Lerberghe takes some turns after a few miles and drops back before you know it. Same with Stybar who is initially in the first peloton, drops back to help a bit, but this doesn't last long. I think he is on camera once, and the next cut, he's gone for good. The hard raced part on the flat, where the front peloton is being paced by the motors, neither Paredes nor Sevilla helped at all. Once the climb starts, it is mainly Paredes together with Evenepoel (Serry is gone by then) who is doing the work. They film Sevilla, as if he's doing some pulls, but right before the image cuts away, you can see at least two other riders in front of him. Regardless of that anecdotal evidence, Sevilla doesn't come to the front to take pulls well after 15k since the peloton tore. In fact, at 26.5k from the finish (when Evenepoel is already taking pulls for 12k) Sevilla is still at the back of the group. Once the climb starts, it is Paredes who does most of the work. In order of total workload Evenepoel clearly did the most work, followed closely by Paredes & Serry, and at quite some distance, Sevilla.
So yeah, from 38k to 20k is miles and miles, especially in these circumstances. It's Evenepoel with Serry vs +/-10 guys of UAE, Movistar & Bohra behind 3 motorbikes. My main issue is with the motorbikes which makes a huge difference at high speeds. Maybe check the other topic and some of the explanation by experts about how much one can benefit from it. In a matter of +/-10-15k, the breakaway which had a 5+ minute lead on the peloton, are caught by the motorpaced peloton. Maybe you think this is normal, but i don't.
EDIT: checked again. The motorpaced peloton closes a gap of 5m25s in 16 kilometers on the breakaway, prior to the actual climb, prior to Sevilla and Paredes helping out. My point being, that this is what he was up against, with minimal support at the time. I'm sure you are aware, that the normal expectations are, that a peloton can gain 1 minute every 10k on a breakaway. Whether you believe the motorpacing was real or not (which it certainly was), it doesn't change the fact that he had to go much deeper than anyone else, over the course of the final 40k of the stage. Had he and Serry kept the same pace as the break, he would have lost 6 minutes or more before the climb even started. Downplaying his achievement is really not necessary.