Yeah, I saw that. The fact different characters will have different thresholds for autosuccess seems to imply different characters might have different DCs, but A) that's a different question B) it's harder to run around the table and C) I'm not sure it's correct or more realistic. I think "harder to run around the table" is reason enough not to do it.
Yeah, I would rather use other tools, like Inspiration, instead for that. The DC generally tells us how likely success is, so it is hard to see a lot of logic in saying "Oh, well, this time Joe is vastly more likely to succeed at this Athletics check than Mike, but yesterday they had the same odds on a somewhat similar check." If there are SPECIFIC REASONS to give different odds, then those must translate to some factor or other that can be explicated, right? Is it proficiency, difference in ability scores, level, some sort of special ability, whatever it is, I'd think it would be better to surface that vs just dictating each character has different DCs.
Now, that being said, if there really IS a reason within the fiction that amounts to something like "This 20th level guy clearly cannot fail, but this 10th level guy just isn't FICTIONALLY at a point to attempt this" there is at least some support for that. I think
@pemerton has stated that is his position WRT 4e and whether a situation is fictionally 'Heroic', 'Paragon', or 'Epic'. It is quite possible, in 4e and 5e both, for characters to MATHEMATICALLY have some chance, maybe a substantial one in some cases, to pass a check that probably should be FICTIONALLY beyond them. I think Pemerton mentioned 'sealing the Abyss' (something that happened in his 4e campaign) as an example of a clearly 'Epic' sort of action. However, I will note that this was a pretty climactic situation in the fiction of that game. Beyond that, how often do radically different power levels of PC compare against the same challenge? In realistic play I don't think varying the DC makes a lot of sense. I'd grant a big situational bonus, or explicate why auto success happened, vs doing that.