What does it mean when "Adoption of MBIT processes" is listed as a feature of a component?

MBIT is a process developed in the early 1980s, quoting from some sanyo document (SY204A):

MBIT : Multi-base island transistor

MBIT transistors are composed of a large number of island-like bases and emitters. As the MBIT structure is an aggregate of "unit transistors", the emitter region is sub-divided and its total area and total peripheral length are increased. This means that these transistors can operate at higher withstand voltages and larger currents. In addition, they operate with uniform emitter current density. The distance between the base electrode and the transistor base itself is short, reducing the switching time

It is merely a marketing hint as to what kind of process was used to judge how reliable its features might be (if you know details about the process involved).

To supplement the other answer, it's a fabrication process aimed at decreasing Vce saturation (so switching losses) in addition to increasing switching speed. That explains why commonly used Sanyo transistors (or clones thereof) in SMPSes use this tech. The marketing department came up with MBIT-II, of course:

Japanese SANYO will not make up BS. SOA improvement and switching time decreasement is the result.

Here's a brochure with original MBIT processed SANYO video output devices: https://drive.google.com/open?id=1PeMaEABg424gjDkrVGHsPrWUxOlHqU50