It is a tap (or splice)... just not subject to 240.21 tap rules because it is a service (or service entrance) conductor tap (or splice), and permitted under 230.33 (230.46). The tap (or splice) conductors must meet all the requirements for service (or service entrance) conductors, including load end OCP. With a fusible disconnect inside at/near the tap, the conductors from there to the outside combiner panel are feeders, and not required to be outside, or installed using a considered-outside method.