Hopefully if more nations stop selling to Saudi it will put a bigger spotlight on US arms sales - kind of shaming them into stopping.
It may not matter to the US, it may not matter much to the victims of those weapons, but it matters for citizens of those countries not selling weapons. Though "freezing" them doesn't say much if you then increase the volume afterwards for a while, but generally speaking, not taking part in something bad is a good in and of itself.