Did Archbishop Lefebvre soften a bit after the election of JP2? Yes he did. He was optimistic that he would be better than Paul VI. Then things soured again at the time of Assisi, which ultimately led to the consecrations.
This attempt to suppress the reality of the "hard line" days is incredibly disturbing. Let the Archbishop speak for himself. He was of course entitled to change his mind, but the truth does not change. He said what he said at the time. Let the record stand. And people are entitled to disagree with him. It reminds me of Orwell's 1984. In addition, he delivered most of these in public, and they were meant for public consumption and edification. While it may be legally permitted, it's not morally acceptable for them to suppress this stuff. Now, if there things in there contrary to faith and morals, then perhaps there would be reason to suppress them. Perhaps the SSPX consider these sermons to be scandalous to the faithful, and are judging +Lefebvre ... all the while exploiting him and the devotion people have to him whenever it benefits them.