Section 310.15(A)(2) mentions the fact that there can be more than one ampacity along a given circuit length.
The four factors mentioned in the Informational Note as affecting operating temperature can also affect the ampacity of a circuit:
Ambient temperatures – There can be different ambient temperatures along the way.
Heat produced by current flow – For some types of circuits there may actually even be different amounts of load current flow because the conductor supplies more than one load.
Ambient medium – There can be different conditions in the ambient medium that would affect the conductor's ability to dissipate heat.
Adjacent conductors – At different places along a conductor there can be different numbers of other adjacent load carrying conductors.