I have no dog in this fight, but the time I checked the extractor had .030" slop, which let the case mouth be what set headspace between the min and trim to length.
I haven't checked this dimension to verify it but development of the "trim to length" has zero to do with the design process which determined the breach face to extractor hook length. dm1906 would argue that the tolerances left in order for the extractor to function properly and for ammunition to feed from the magazine to chamber reliably make the shoulder in the chamber irrelevant. Actually, the shoulder is machined the way it is to limit forward motion of the case during the firing sequence. The extractor was not designed for this purpose. Although a byproduct of it's method of operation and may provide some benefit in this area, the intended mechanics of the operation of the pistol does not include the use of the extractor for this. That being the case the manufacturer never designed the extractor with that in mind. dm1906 would propose that there is no minimum case length specification at all as long as favorable dimensional relationships between the extractor hook, case extractor groove and rim and breach face are maintained. The chamber's shoulder is of no particular significance and could and probably should be deleted as obsolete.
I am not of that particular persuasion and must therefore just agree to disagree.