Only clear overlap imo is on paratroopers. Paths don't overlap because IR Paths are often used to great effect while Pathfinders are very seldom used and much worse. Tech flexibility is kind of inaccurate since the combat group is more appealing for its huge value for cost than for allowing you to skip the full Captain tier, so I'd say there's a bit of overlap there but also a fundamental difference.
I wouldn't say that's bad, there's a lot of doctrines that overlap a lot, such as Strategic Reserves and Mechanized Assault for example.
Tech flexibility is there because Reckon allows both pack and light vehicles access regardless of tech path.
Overlap might be a good or bad thing but my point is that currently this overlap seems to make Reckon chosen over Airborne. There far less overlap between mechanized assault and Strategic reserves which ends at assault grenadier (although one could make a case for Tiger and Tiger ACE).
My point is that if one wants to make Airborne more attractive one should probably change the Reckon also and removed some of the overlap.
I have actually made some suggestions about this.