Well every time that Ruth's name is mentioned in scripture, it is followed by the adjective "the Moabitess", except for Matthew 1. So then does that mean that the "Ruth" listed by Matthew is not the "Ruth, the Moabitess" in the Old Testament as well?
Matthew does not include that adjective "prostitute" beside Rachab's name because after the fall of Jericho, she was no longer a prostitute, and she was certainly not a prostitute after Salmon took her for his wife, and most certainly not after the birth of her son.
The Israelites were not supposed to do a lot of things according to the Law of Moses, but they did them anyway, and God used even their disobedience in His plan of redemption. And a Jew [Israelite] was a Jew [Israelite] from the inside out not the outside in, and Rachab and Ruth had more of a heart for the God of Israel than probably most Jewish [Israelite] women of their day.
God sees the heart and He saw it in these case and rewarded them both with Jewish [Israelite] husbands and sons, through which they were sanctified into the congregation of Israel.
She "was" a Moabite woman because she lived in the Israelite territory of Moab.....not the Kingdom of Moab. There were no genetic Moabite people left here. The King of the Amorites saw to that and then Moses took "The Plains of Moab" away from him. This was part of Israel for over 700 years and it was still called Moab.
Matthew does not include that adjective "prostitute" beside Rachab's name because after the fall of Jericho, she was no longer a prostitute, and she was certainly not a prostitute after Salmon took her for his wife, and most certainly not after the birth of her son.
The reason for this is very simple. Matthew is not referring to the prostitute....James and Paul are! Rachab was not Rahab.