I've been following this guy's YouTube channel for almost a year now and have some thoughts.
1. I don't think any of us has a clear idea of how much aerobic development someone might be able to gain from doing over an hour of pullups per day. In some of his videos, he shows his heart rate after a set, and it generally seems to be around zone 2, so there's certainly some cardiovascular benefit to high rep pullups that needs to be understood as a benefit to endurance events in general.
2. He does have a running background, although his high school times, based on what can be found online, are nothing to write home about. He doesn't appear to have significant running talent.
3. His physique compared to videos from just 2ish years ago is significantly bigger looking. Some of this could be leanness, but PED's could also be a factor.
4. To be highly successful at pullups and running, carrying the level of muscle mass that he has, particularly in the chest and front-delts is extremely suspicious as an indicator of PED use. High level rock climbers would likely have a physique similar to what extensive pull-up training would garner, and they look nothing like this. Androgen receptors are disproportionately in the upper chest/shoulders, which look to be overdeveloped without any obvious amount of high-level training to those areas in particular.
5. Running high mileage and doing pull-ups for endurance are not anabolic activities. I'm 6', 180, with a relatively high muscle mass. Even running 30+ MPW, I quickly drop to 170 lbs and do not really look like I lift weights at all. He has been working out longer, and more intensely than I have, but the muscle fullness at this level of training is abnormal for someone not on PED's.
6. Recovery/durability from this extremely high amount of exercise is indicative of PED use.
Yeah the guy works hard, and he looks great, but if you think that you can accomplish this without using PED's, you're going to be disappointed. It's always possible that he's an absolute genetic freak and doing it without gear, but the evidence based on what he used to look like and his past running performance don't point in that direction.