I would say the main difference is in the conclusions drawn by authors — Radchenko (FA) conclusion was that the peace deal was „nearly there” but Ukraine cancelled it under pressure from UK-US. Szeligowski and Kumoch conclude Russia never participated in these talks to negotiate and peace deal, they just came for Ukraine’s capitulation. Based on the diplomatic context they provided, not just reading of the various drafts, their version is much more fact supported — Radchenko’s selective reading of the draft alone misses this whole context.