Q. why are parts of the history of the church (HC) used as scripture, but it is not "sustained" as scripture and not searchable online on lds.org?

i find it strange/confusing/disappointing that references from e.g. the bible dictionary cite parts of the HC in an authoritative manor:

In latter-day revelation we learn that the angel Michael is Adam, and the angel Gabriel is Noah (HC 3: 386).

but it is not a part of the churches official scriptures and is not searchable online on lds.org.

udpate: maybe it has something to do with this:

But Jerald and Sandra Tanner, who are noted for their research on Mormonism, point out that
about 60% of the content in the History of the Church was not completed during Smith’s lifetime
(Falsification of Joseph Smith’s History, p. 22). Therefore, Smith couldn’t have written many of
the things ascribed to him in the DHC.
Mormon historian, B. H. Roberts, and those who helped him compile the DHC actually copied
information from other peoples’ journals and put into the DHC to sound like Joseph Smith wrote
it.