The author of passage A argues that even though concerns regarding independent research at the trial level "have some merit", independent research may be valuable in certain cases, such as scientific evidence context. The author of passage B argues that independent research is never appropriate at the appellate level.
The issue with (E) is that it would be improper to characterize passage A as "forceful advocacy." The author acknowledges the opponents' concerns and argues that there are certain cases where judges could benefit from independent fact-finding, suggesting that the author approves of independent fact finding but only in specific instances and within the structure of the trial, thus "qualified approval" is a more apt description of this attitude as (D) suggests. Another issue with (D) is that the author's opposition in passage B is not tentative. He is firmly against any fact finding at the appellate level -"appellate courts should resist the temptation to conduct their own research," and uses the rest of the passage to outline his reasons why. His opposition/ noncommitment is explicit and absolute, making (D) "explicit noncommitment" a better choice.
Let me know if this makes sense and if you have any further questions.