It's hard to be sure without a living author to ask for clarification, but here's a few possibilities, guessed at based on the surrounding text and by the context provided by Winn and others elsewhere in FREE SOCIETY. It was fairly common in the social anarchist milieu of the time to contrast accumulation of resources for personal use with accumulation for any of a few different purposes: (1) accumulation of resources for profit motives, which could mean either (1a) accumulation of resources in order to rent them out to others (broadly understood to include not only leasing property but also loaning it for interest, investing it for income, hiring employees to work it for you, etc.) or (1b) accumulation of resources in order to profit from them in the market (by any means, rental, investment, sale or otherwise); (2) accumulation of resources to defeat rivals in social or economic competition; (3) accumulation of resources for social status, display or idle luxury; (4) accumulation of resources as reserve savings, in order to ward off the danger of penury. (*)

It's not clear to me which of these Winn meant to refer to. The references to dependence and the fear of poverty might seem to indicate (5); but they might also be referring to (1a/b) on the claim that without consumers who have been driven into an artificially desperate position there would be no market for the accumulated wares. The references to "commercialism" and "the greed of gain" might seem to point towards (1a) or (1b), but (2) or (3) might also be in mind if Winn is trying to take into account broad shifts in personal and cultural priorities that might result if people are more broadly economically and socially independent. My best guess is that he quite possibly meant (1), or quite possibly meant (4), but that the other 2 options are all relatively plausible candidates too.

Anyway, it should be clear enough that of these different claims, some are more likely to be simpatico to market anarchism and others are less likely to be simpatico. (So, e.g., someone like Tucker or Lum would want to draw a pretty sharp line between 1a and 1b, you might want to seriously nuance 2 in light of different kinds or senses or contexts for "competition," etc.) Certainly they are all explaining a slogan by reference to other slogans, and there are a lot of conceptual problems that need to be sorted out (like about what counts as "use" or idleness in the first place, who gets to make judgments about productive use vs. "luxury," what is or is not being considered as a form of savings or investment or profit, and a bunch of other stuff.) That said, whatever the right answer to this may be, one of the really important things to track is going to be the way in which Winn's argument draws on a strong appeal to a specific ideal of economic individualism in order to recommend his picture of a liberated society (because the stated goal is specifically individual independence, right? and the analysis has to do with the ways that removing political privilege will allow folks to peacefully route around particular forms of social conflict, dependence-traps and poverty that get in the way of that). So there's something I think for market anarchists to think through and discuss and to chew on even if it's not 100% stuff that we'd want to swallow
at the end of the day.

Hope that helps clarify at least?
My recent post Your General Assembly will always be Incomplete.