Never used MLO but can comment on preference for extensive hierarchy.
Everdo is a fantastic and pureist implementation of GTD. The key is in the name - Getting Things Done. It is a system designed for task completion and therefore works from the bottom up, with less consideration for how well does something link to higher horizon goals - or not.
In contrast the more hierarchical approaches are top-down and lean towards “Dropping things that shouldn’t be done”. Take something as simple as an Eisenhower/Covey matrix - 75% is about stuff that you should delegate, delay or drop altogether rather than do. When you throw in folders/projects on top of that, then all the fiddly bits and needs to rejig increase dramatically with the amount of “fluff” i.e. the more stuff that does not have a direct link to Horizon 5 or 4 items.
One is more about efficiency the other about effectiveness. They both have a role