The submission editor can display contextual help while editing, accessed by clicking the little question-mark icon next to the field, in the desktop browser interface.

When editing biographical data, the help displayed still extensively discusses the old

Worse, the links displayed point to the Linking names and titles in text based lists help article, which has been updated so that it now makes no mention of
Please update the contextual help texts.

When editing biographical data, the help displayed still extensively discusses the old
(qv)
syntax for linking, with no mention of the new [link=nm#######] / [link=tt########]
syntax that is (as of November 2017) the only supported syntax for creating links in submission data.
Worse, the links displayed point to the Linking names and titles in text based lists help article, which has been updated so that it now makes no mention of
(qv)
syntax.Please update the contextual help texts.
Jeorj Euler
FeRD
FeRD
Anyway, what I HAD previously written was: I assume the system uses the entire contents of the posts in computing similarity / mutual relevance, so there's a lot more for it to go on after I've submitted than in just the initial question. Once it has all the details, THEN it can find the duplicates.
Still frustrating, though.