It seems that he's mostly considering the value of the idea of economic rents in terms of how well they explain corporate profits as a means of testing the idea of economic rents themselves. However, the core idea of economic rents comes from analyses of land rents and monopoly rents in the 19th century: application to contemporary corporate profits is a derivative application of the idea.

Land rents, for example, were the rents generated by idle 18th and 19th century gentility simply for inheriting the land at the basis of economic production in an agricultural economy, rather than for contributing useful labor towards agricultural production. This idea has gained renewed attention with the rise of extreme inequality and inherited capital.

He also seems to be conflating these different kinds of rents together: land rents, monopoly rents, IP rents. The economic value of IP rents can be easily seen in patent trolling, defensive patents, &c. But trying to explain the corporate profits in terms of unspcified "rents" sound more like a project to discredit the idea of economic rents by conflating a lot of variables. That might be because I'm skeptical that economic rents are a predominant explanation of rising corporate profits, of course.