How about 240.4(D)(3)???? it says unless specifically permitted in 240.4(E) or (G) you cant OCP higher then 15 amp on a #14. This is not a tap if it is a multi outlet branch circuit.
The problem that will occur over time is when the outlet is overloaded the 14 will have the insulation harden and fall off causing an eventually failure in the circuit that could lead to a fire, This is not just my opinion it is a situation I see frequently in older homes.
Don't forget that just because one article of the code makes it seem as if you could do this it still doesn't override article 240.4(D) unless there is a specific article allowing you to ignore 240.4(D)
There is... 240.4(E) Tap Conductors renders 240.4(D) moot, and a full 20A rating of 14 AWG can be used.
Of course this portion of a branch circuit must qualify as a tap first per 240.4(E). Per 240.21(A) the requirements of 210.19 and 210.20 must be satisfied (which includes satisfying 210.21 for outlet devices).