I wouldn't call the non-North American models a "version" or "variant" of ST1100, as that implies to me much more than just a different marketing approach for those markets in which "Pan-European" has a direct resonance.
1. There are model differences in ALL markets in which Honda sells motorcycles. Such differences relate to lighting, emissions and marketing, as noted above, as well as available colours, labeling and power output. These differences are reflected in the frame numbers or VINs, which differ for each such market. As noted above, the character following the "SC26" in the VIN, is used to indicate the market for which a particular model was originally manufactured. US models have a Model Code of "SC260", California-spec bikes have "SC261", Canadian bikes "SC262", Australian ones "SC26U", and so on, for European Direct sales, Germany, France, Switzerland (due to emissions laws) and (depending on the particular Model Year) sometimes Italy (used to have a single-headlight requirement), Austria and various Nordic countries. The exact codes are all listed in the front of the relevant Honda Parts Catalogue, and on some of the online microfiche (if they bothered to scan those pages--and depending on whether the source was the US-spec Parts Catalog or the ROW Parts Catalogue). In addition, when Honda made an optional ABS or TCS variant available in the same year, this too required a different Model Code to indicate that. Accordingly, each different market-specific model (and ABS variant) of ST1100 was represented by a separate Model Code (and, in many cases, separate serial production numbers). There must have been at least a dozen ST1100 Model Codes, and there have been, AFAIK, at least 12 different ST1300 Model Codes to date (4x US-spec, 2x Canadian, 2x Australian, 4x European), plus Police models...
2. In addition to a market-specific Model Code, each Honda model also has a specific Model Name and, often, a separate Nickname. I don't think Honda uses these terms, but that's how I have come to think of them. I would classify "Pan-European" as a Nickname, like "Interceptor", "Hurricane" or "RC51" in the North American markets. Nicknames are used purely for marketing purposes and sometimes do not appear in the Honda Parts Catalogues. Model Names are the familiar alphanumeric names that do appear in the Honda Parts Catalogues. For example, the Honda Parts Catalogue for the European-spec ST1300/Pan-European says "ST1300 / ST1300A" on the cover, not "Pan-European". That suggests to me that the legendary European-spec sport touring bike in question has both an official Model Name as well as a Nickname.
3. Of the more minor differences between Model Codes, surely the badges indicating "ST1100" and "Pan-European" are among the most minor. (I bought Euro-spec Pan-European fairing badges and instrument cluster lens for my US-registered, European-resident US-spec ST1300 because I like confusing people...

)
4. My own personal view is that American Honda Motor Co., Inc. chose not to use the "Pan-European" Model Name on the ST1100 and ST1300 because they did not want to confuse American buyers with strange-sounding "ferrin" geographic references, but this also may have been because
they were unsure what it meant. <GD&R>
Ciao,