biometrics said: "reverted right back to the apostate doctrines that commentaries by Christendom"
I agree with the thoughts that some others have mentioned. The terms "Christendom" and "Christendom's commentaries" and the like are simply WT loaded language.
Whenever the WT sites some non-WT reference (and of course, they don't usually give where it comes from), but if it agrees with what the WT is saying, then, it is from a "Bible scholar" or a "Bible researcher." But anything disagreeable comes from "Christendom's commentaries" or "worldly publications" and the like.
The fact is, most WT publications come from Christendom's commentaries. For example, the historical information in the current Book Study (Acts) follows fairly closely with the NAC commentary on Acts (Polehill is the author of that one). What you will get in a decent academic commentary, that you won't get in a WT commentary is: alternative views and the reasons for those views, copious notes with references to other books, and, generally speaking, a complete lack of the "we know best" smug arrogance that is typical of WT pubs. When there are possible alternative views, WT pubs tend to pick one that they go with and never mention any others, or glibly dismiss them as unreasonable.
For example, within the last few years, the Society has come up with "new light" on some of Jesus' illustrations in Matthew chapter 13. Many of the old understandings were based on W. E. Vine's understanding of these (although the Society never owned up to that). But if you compare the "new light" explanations with recent academic commentaries from "Christendom," you will see that for the most part, they now agree with what "Christendom" has been teaching for many years. How about that! Even the Society has reverted right back to Christendom's "apostate doctrines."