I may have some reservations about the accuracy and completeness of the quotes, but for the sake of argument, I will play along.
. . . and that the people who spoke or wrote them were:
1) Mormons who were high ranking officials in the Mormons church;
OK, that is undoubtedly true.
2) Probably had more authority to speak on Mormon Doctrine than you; and
Since I claim no authority, I have to agree.
3) Actually believed that what they wrote was consistent with what the Mormon Church taught at the time?
I think so.
However, I would also add:
4) Those high ranking officials often presented their own opinions, which they (and their listeners) recognized as such;
5) Those high ranking officials sometimes disagreed with each other;
6) As members of the LDS Church, we are obligated to support the current President of the Church, and not past leaders;
7) God is the ultimate authority.
I suspect that sets the boundaries for the debate.
That being said, if Gordon Hinkley stands up at the General Conference and explains some Mormon Doctrine, can we assume that what he says is the current teaching of the LDS Church?
Can we quote him when we say "The Mormon Church teaches..."?
And can we then quote what the prior prophets have spoken and say "At one time The Mormon Church taught..."?