Chet, this is not a hill to die on, but let me offer an alternative way of looking at this. Rather than God relaxing laws and then tightening them up again, let's look the new community God formed in the church, compared to the old community of the nation of Israel. For I would suggest to you that nothing has changed in God's approach to divorce, but rather the community dynamics have changed.
Israel was (and is) a nation, while the church is a community of believers assigned to reside within nations and under their authority. Israel had national governmental responsibilities, while the church relies on the nation of its dwelling to handle legal governmental matters. Thus the church deals with moral issues, while the government deals with legal ones. But Israel had to deal with both, and generally speaking the laws of Israel were government laws as well as moral laws, and therefore had a wider range of issues to address.
Currently in our society in our nation, divorce is legal but considered immoral in many cases by the church. In Israel divorce was also legal, but in many cases immoral in God's eyes. The divorces that God permitted legally, were still immoral in many cases. And I'm not sure that the church today should lobby for the illegality of divorce in our country. But we certainly should continue to speak out on moral matters concerning marriage and divorce. But unlike Israel, we differ to our nation's government to handle the legal side of it. But from God's perspective, I don't see any change.
Just some thoughts.