As usual, it is a matter of definition. Mormonism uses “Christian” in two ways. One, as a definition of what their leaders have called “so-called Christians”. In this use, “Christian” has a negative meaning, and represents everything that Mormonism seeks to “restore”. It goes with labels like “the great and abominable church”, “the church of Satan”, “Babylon”, and the “whore of the earth”.
The second usage, which is the “calling themselves Christian since 1975” version, is where Mormonism has redefined Christian to mean “restored Christianity”, in other words, themselves. When Mormons say they are Christian, they are NOT saying they are Christian as all of Christianity understands the meaning. In this usage it is a relative term, covering anyone who has a positive view of Jesus Christ, no matter how Mormon that view is, or from a Catholic view, how orthodox that view is.
The early Mormon church leaders purposely distanced themselves from Christianity. Brigham Young was adamant that Mormonism was not Christian, because his view was rooted in the first understanding. The great and abominable church, which Mormons will say they are the remedy for, not a part of.
As I said, this doesn’t endear them to the Christian populations they hope to convert, so there is a softer sell of Mormonism today, and Christian to Mormons now means “We love Jesus too!”.
In this way, they are accepting Christianity as Christian, rather than defining us a “the whore of the earth”. In that sense, it is a HUGE change for Mormonism.
I once asked a Mormon if this means they viewed an atheist who has a positive view of Jesus, as being a Christian, and she said ‘yes’.
So, there’s where they are at, never mind that they worship a different idea of God, and spend a considerable amount of effort mocking the God Who Christians worship.