1\newcommand{\WPabstract}{%2Can product-level online catalogues reveal the spatial organisation, diversity and specialization of a regional retail economy beyond what business counts show? We study one read-only snapshot (1 November 2026) of Fabri-Ka, an aggregator of the public catalogues of 1{,}569 Quebec-based online stores (390{,}108 published listings, 17 administrative regions), with a preregistered design in which every regional statistic is confronted with a null that reallocates merchants rather than listings. After cleaning (370{,}054 listings, 1{,}557 stores) and recovering merchant locations from official geography, we find that regional specialization is a property of merchants, not of listing volumes: under merchant-equal weights the region--category dependence exceeds 2{,}000 merchant reshuffles (Cramér's $V$ 0.111 vs.\ 0.086, $p<0.001$) in every sample variant, whereas under listing weights it is indistinguishable from chance ($p=0.21$; $0.45$ after trimming the largest one per cent of stores), because catalogue sizes are extremely skewed (Gini 0.85; the top decile of stores holds 79\% of listings, with a power-law tail). Rarefied assortment diversity spans a narrow range (0.73--0.89) and shows no detectable association with population, business counts, income or density across sixteen regions. On 1{,}064 matched products sold by several merchants (matching precision 0.90--0.92), posted prices differ by a median of 4.7 log points; region effects are jointly significant under a wild cluster bootstrap ($p=0.005$), and resellers post prices 11.6 log points below producers' own shops ($p=0.001$). An ECI-type complexity indicator fails its preregistered bootstrap validation (median rank correlation 0.67 on a $17\times20$ matrix) and is withheld; the Quebec Digital Assortment and Complexity Index is published as separately validated components only. Measurement is central: the platform's keyword category labels reach 46\% precision against annotator consensus and are replaced, by a rule fixed in advance, with a classifier validated at 88\% on a held-out audit; a fifth of listings have no recoverable location; coverage per thousand business locations varies six-fold across regions because discovery runs through regional directories. A local-origin price premium is untestable in this source. All code, audits, decision log and amendments are released.%3}4