You gotta see how that’s more complex than 5e’s DCs and also not needed in 5e? Like, a level 1 can hit DC 20, and a level 20 can fail DC 20. Everyone is within that band. No need to look at charts or tables, you just judge difficulty by the measure of an average person, and then go. The level 13 Rogue just succeeds on lots of checks, and is more capable of attempting things that would be impossible for the average person.
Actually, I'm not even that interested in descriptions of 'difficulty' as abstract from level anymore. HoML has a very simple chart, it indicates a DC for each level (I call them DVs, but whatever). So you simply say "this is a level 5 task" and in comparison to your own level you will know what to expect. Tasks of your level are normally achievable results which are non-trivial but within reach of any PC of that level. If you go up 5 levels, you have a task that is unlikely to be achieved by a character without any additional bonuses, and if you go down 5 levels the tasks should be effectively too easy to dice for in most cases. It works great.
Additionally the bonus model is pretty close to 4e in general terms. There is a linearly increasing bonus and DC increase which keep pace with each other. Every PC will get a bit better at most things, though they will lose some ground vs specialists at higher levels, and those specialists will be even better at relatively equivalent difficulty tasks than at level 1, though again not be a vast amount.
OTOH there are only 20 levels in HoML, which has SOME similar effects to BA in that the level range where things can be taken on is about similar to 4e, but since it is in a 1/3 smaller total range from "newly minted hero" to "demi-god" you can take on more of the game's elements at any given level, as a percentage. That is a 5th level PC could interact with level 1 stuff (very easy but could trip you up now and then) to level 10 stuff, which will be Legendary monsters and such, though certainly not the very deadliest/toughest of them (and Mythic stuff is still well beyond you, you're not going to toss with gods as a level 5 Heroic figure).
And those differences are a major way in which a group will determine whether to play one type of game or the other, and whether it’s better to hack one game or switch to another game.
I am not sure I understand what you are even trying to say here. I would simply reply that the system as you conceive it doesn't seem to have any switches at all. Yes, you can make it pretty much impossible to pass most checks for your PCs, so can a 4e DM or myself running HoML.
The real 'dial' in any case is not the DCs it is THE FICTION. So, if you depict level 1 PCs climbing trees, then how that plays out is, the top level could be PCs climbing Mount Everest, or it could be the PCs climbing Mount Celestia in the middle of a huge storm while being assaulted by Storm Titans. One will make the PCs look tough, the other will be almost godlike Mythic heroes writing themselves into the history books. Of course, the numbers will be the same either way. I think it would be hard to do that with 5e, there is simply not a great enough range of numbers for the later scenario to work. It is pretty much casting itself as a game which can only depict action that matches things real people could attempt (at least in the ability check realm, combat is a whole other story).
Now, you can tweak other dimensions of the game as well, but it is a LOT easier to have a single 'dial' there. That was something I liked about 4e's approach, and why in some ways it is really a very flexible system.
@Manbearcat I think I'm disputing your last post here
