That's not the point. This is about the new possible 2017 NEC 210.12(A) language for branch circuit extended from a "listed overcurrent protective device" to an Outlet Branch Circuit AFCI device.
As worded, a new branch circuit may be extended from an existing fuse center, using the 2017 NEC 210.12(A) allowed wiring methods between the fuse and the OBC AFCI, and that seems, by the proposed 2017 language, to provide what the 2014 system combination AFCI + matched OBC AFCI intended.
Any OBC AFCI seems to have become EQUAL in "AFCI ability" to any combination-type AFCI circuit breaker.
I doubt that a change in plain-old circuit breaker magnetic trip thresholds has anything to do with why fuses are proposed to be allowed, in lieu of the 2014 NEC "system combination AFCI + OBC AFCI", to equal a combination-type AFCI.