Foreign Tax Credit Category for Pension Income

Does anyone have access to the BNA Tax Management Compensation Planning Journal?

I recently stumbled on a reference to the following article, which I am interested to know more about:

Veena K. Murty, Selected Cross-Border Equity and Deferred Compensation Issues With Funded Foreign Plans, 42 COMP. PLAN. J. 67 (Apr. 4, 2014)

The reference was in the footnotes in the article "Migrants with Retirement Plans: The Challenge of Harmonizing Tax Rules" (17 Florida Tax Review 1), which I found here. The part I am interested in reads as follows:

In addition, the United States applies the limitation separately to general category income and passive category income. I.R.C. § 904(d)(1). See Murthy, Cross-Border, supra note 28, at 9 (suggesting that distributions from a section 402(b) trust, including amounts attributable to earnings in the trust, should be classified as wages, despite the contrary rule applied to earnings of a U.S. tax qualified plan, which are treated as investment income sourced by reference to the situs of the trust).

This reference makes it sound like whether a pension plan distribution goes into the general or passive category for purposes of the foreign tax credit depends on a multitude of factors, potentially including what portion of the distribution is from the earnings of the plan. This is not something I've ever heard of before. I've heard a number of differing opinions on whether pension distributions go in the passive or general category, but nothing like this.

Reference is made to a "rule" that treats earnings from a U.S. qualified plan as investment income. What "rule" could they be talking about?

Finally, what category does everyone think the pension distributions should go in?