I also checked the Pali text of the Sutta, and there is no mention of ‘atta’ at all, just attha.
I downloaded the Pure Dhamma book where Venerable’s arguments are listed and further developed. Right now, I may tell you that equating atta with attha (using the modern Sinhala meaning of all things!) is mind-bogglingly bad linguistics, it is just so bad one can only facepalm, so I presume you meant the post in a humorous way I will definitely read the book for a good laugh and therapeutic eye-rolling. If you want to find out why it is so bad just look up the etymological data for attan and attha in the Pali Text Society’s Pali-English Dictionary.
Not sure if you are asking me, so just in case I’ll answer The lexical meaning is explained the Pali Text Society’s Dictionary. I am no Pali scholar, so I cannot say if the explanations can be approved upon, but they make sense, and even my relatively sparse knowledge of Dhamma ad Pali tells me that the Pure Dhamma interpretation is linguistically pure nonsense. As for the doctrinal exegesis, I would say that the Attha Sutta is pretty straightforward: ‘These things are good for you, so strive for these things,’ while you can write quite a lengthy book on the Anattalakkhana Sutta as it deals with the non-self doctrine.