I am a Protestant (I can hear you going “I think we found your problem right there”) and don’t have a dog in this fight, but there are some things in scripture that support the idea that his framework of one community inside and one outside the garden is correct.
The blessing God gives to mankind in 1:28 does not sound like the conversation He has with Adam and Eve later on. The Hebrew on the words “dominion” and “subdue” have connotations of treading down and conquering. “Subjugate” might be a way to say it. That is very unlike the garden where the LORD God did all the work and the animals did not need subjugating and the ground only needed tending and keeping.
Further, the command to be fruitful and multiply was the first thing mentioned in chapter one. In chapter two its almost an after thought!
This doesn’t figure into his model, but it does figure into mine which shares the same framework of two communities, but in 1:27 there is no mention of “male and female” being created in the image. Only THE man (in the Hebrew its there) and the echo of that which uses a singular pronoun. This hints at a community which is not yet a part of the fellowship between the LORD God and the Man, with fellowship being a requirement to fulfill the human capacity to bear the image.
None of that in chapter one is explicit I will grant you, but 2:1 is explicit. It describes what God had just done- create the “host” of “them”. Them being heaven, and earth. Look up the word “host”. It refers to an assembly of sentient beings capable of military action (like subjugating the earth). Sometimes it refers to the heavenly bodies themselves but isn’t it so that the stars were identified with heavenly beings without distinction?
So God created a “host” on the earth according to Genesis 2:1. That military language fits perfectly with the mission He gave to humanity in 1:26 and 1:28 but is a tall order for a single couple.
All that is before the standard arguments you hear about Cain’s wife and even more telling, that Cain acted like he knew that he was not the first murderer in the world and was terrified that “whoever” would kill him if he were cast out of the family fellowship.
So like I say, I don’t have a dog in the specific fight of whether the Catholic church accepts GA as a possibility, because I am neither Catholic nor is the Christ-centered model a perfect fit with GA, but if it is rejected let it not be because there is nothing in scripture to suggest it.