No, it is only good for the main feeder and to other panels within the same dwelling. Conductors feeding a detached "shop" must comply with 310.16. So it's ok to run #4 copper feeders to a subpanel on the 2nd floor of a dwelling for 100 amps, but if 100 amps is desired for a detached shop, #2 copper should be run.
Shock, a sub panel is not a "main feeder" unless that is the source of all current to a dwelling. For example, if you had a 100a disconnect at ther meter feeding a distribution panel that would be a main feeder. If you come to a main panel with other loads and then feed another sub, that is not a main feeder and you us 310.16.
A main feeder, and all other feeders within the same dwelling, shall comply with Table 310.15(B)(6).
Not sure where you are getting this from. 310.15(B)(6) can't be used for subpanels.
310.15(B) (6) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders For individual dwelling units of one family, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(6), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service lateral conductors, and feeder conductors that serve as the main power feeder to each dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. For application of this section, the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch-circuit panelboards(s). The feeder conductors to a dwelling unit shall not be required to have an allowable ampacity rating greater than their service-entrance conductors. The grounded conductor shall be permitted to be smaller than the ungrounded conductors, provided the requirements of 215.2, 220.61, and 230.42 are met.