You’re just creating more supposition where there is none. The reporter said he got it “thus and thus” and now you posit that “they” knew all along what and where it came from. Both patently cannot be true. I don’t buy it.
As for just the front pages, that’s all that’s needed. It shows the income, the deductions, AGI, and the taxes. The rest is merely backup to justify the primary numbers on the main form.
"The rest" is really what they're looking for. If he had $80 million in expenses paid to contractors, the identity of those contractors (from the copies of the 1099 or similar forms for them) would likely be of great interest to people.
You didn't address my other point: How did they know it was a real copy of the return, and not a fake?