My goodness, there’s so much wrongness here it’s hard to wade through it all.
Apart from the many good points made in the comment linked by @mikenz66, I would like to add a little more about Buddhaghosa.
The facts about Buddhaghosa have been well-presented by Bhikkhu Nyanamoli in the introduction to his translation of the Visuddhimagga, The Path of Purification. Anyone who is interested should start there: it is an extremely well-known and widely available text, and there is really no excuse for not being familiar with basic details.
The idea that Buddhaghosa was a Vedic scholar is nonsense. It stems from a late hagiography. One of the standard features of later Buddhist hagiography was to claim that any teacher was a former brahmin who became converted to Buddhism after being disillusioned with brahmanism; see Moggaliputtatissa et al.. This doesn’t mean that none of them were brahmins; brahmins were around, and some of them no doubt did convert. But it means that a claim in a book written centuries after someone lived has zero credibility, unless it can be independently corroborated.
Normally any such claim would require support in the genuine contemporary texts, and in this case the only real witness is the work of Buddhaghosa himself. Now, given that he gives thousands of pages of detailed commentary on doctrinal and linguistic matters, it should be pretty easy to see whether he is smuggling in any kind of hidden Vedism or brahmanism.
But no actual scholar has ever made such a claim. Rather, everyone agrees that Buddhaghosa was exactly what he claimed to be: an editor and translator who compiled the ancient Sinhalese commentaries into a more consistent and modern form, while making only very occasional and minor suggestions himself. Anyone claiming that Buddhaghosa introduced any major doctrinal innovations flies in the face of all the scholarship in the field.
This means that, unless there is evidence to the contrary, anything found in the commentaries should be assumed to have been apart of the ancient Sinhalese commentaries. That doesn’t mean it is right, it just means that it should be seen within the context of the development of Theravada Buddhism in Sri Lanka. And there is no evidence that there was a pro-brahmanical trend, or indeed even much awareness of the brahmanical texts at all.
On the contrary, the PTS dictionary—published nearly a century ago, and one of the best-known and most important source works in the field—pointed out that the commentaries explain the Pali term vissa incorrectly. Vissa is the Pali form of the Sanskrit viśva. In Sanskrit, there are two words for “all”, viśva and sarva, both of which are very common. For some reason, only sarva is found in Pali, in the form sabba. But occasionally we see the form vissa. Now, anyone with an elementary knowledge of Sanskrit would immediately know this word. But the commentaries explain it incorrectly. It’s inconceivable that any kind of brahmanical scholar would make such a mistake.
This is far from the only example. In my studies, one of the most persistent kinds of flaw I have noticed in the commentaries—a flaw that persists in modern scholarship—is the lack of knowledge and awareness of the brahmanical context. Almost always, things that are responding to brahmanical teachings are explained with a purely Buddhist context, so that a dialectical response becomes an absolute statement. The real problem with the commentaries is that they had insufficient knowledge and understanding of the brahmanical context to which the Buddha was responding.
I might add as a further point that in modern Buddhist studies, we lack good critical scholarship of the commentaries. Most of us focus on the suttas, which is of course important. But that leaves the commentaries mostly to those who identify with the Theravada school, and see them as identical with the suttas. This allows criticisms of them to gain traction, even done as crudely as we see here. Of course, there are plenty of things to legitimately criticize about the commentaries. But no serious scholar indulges in this kind of dismissive and conspiratorial thinking. I have some knowledge of the commentaries, but not much. It would be nice to see more serious work done in this area, since the commentaries inform much of the practice of contemporary Theravada.