A few thoughts: first, I have had an experience where my watch got the elapsed time wrong. By like 45 minutes. I was on a ride with my Garmin Forerunner 25. About 75 minutes in, the GPS added one point way out in the middle of the Atlantic Ocean. Just one point. The rest of the right location was correct, but that one stray point added 45 minutes to my ride. Bizzar. I think I may still have the original file, although I ended up fixing it with various tools online. I had to crop the first half of the ride, re-upload and crop the last half of the ride, then merge the files using one of the GPS tools online. The overall time is still wrong, so it looks like I took a 45 minute pit stop in the middle of the ride, which I didn't.
Second, tools online give you the ability to mark up the GPS file and change what device recorded the activity. I could take my Foreunner 25 file and make it look like a Wahoo recorded it.
This, if Dane was to cheat with the file, why not just use a tool to time shift the file to the start time of the marathon? That can be done, too , online. I could take a ride from 2017 and re-timestamp it to look like I rode it yesterday. Not that hard.