The Internal Revenue Code is made up of chapters, one of which is "Income Tax". That chapter is made up of subchapters, two of which are C and S. Subchapter C is corporate taxation. A "Subchapter C" corporation is the same as a "C" Corporation, and either designation is appropriate when distinguishing it (a taxable C corp) from a corporation whose tax status is changed by a different subchapter.
Subchapter C also contains rules on dividends and earnings and profits. Like Need High Yield, I couldn't find justification there for treating the Pfd Stock distribution as a taxable dividend. Then again, if someone was paying me big bucks, maybe I'd look a little harder. Unlike NHY, I defer to the hired guns.