Do not buy that. Paul tells us that all scripture is inspired and profitable, 2 Timothy 3:14 – 17. John tells us that the Holy Spirit will lead us into all truth, John 16:13. If it were the case that you would need secondary history sources to profit from God’s Word. Those verses would read differently perhaps the 2 Timothy passage would read something like, “All Scripture is inspired by God and profitable after you read all of the commentaries on the book and fully understand the historical context then it will instruct you…” But it does not say that, does it.
You can benefit from God’s Word just by reading and observing the text.
You know if it is important, God probably put it in the text. A quick example. In a session in another country we were studying 2 Peter. It was observed that the book was written close to the end of Peter’s life. One of the men asked how he could find out how old Peter was when Peter was killed. He said it would help him understand the text better. I pointed out that in several cases that God did tell us how old people were when they died. Genesis has a number of them. But He does not tell us how old Peter was. I suggested that apparently it was important to know how old Adam et.al. were when they died but not Peter.
The point is that God has put what we need to know in His Word. The secondary sources can help sometimes but they are not necessary and frankly can in some cases be a problem.