Notation: Slurs with little lines at initial/end points

Does anyone have a definitive explanation from a publisher or authoritative source regarding such a slur (or at least personal experience)?

For example:

The extract from which this was drawn also utilizes slurs without these small lines, and so it seems not to be equivalent to a regular slur's usage according to the composer/publisher.

As an educated guess, I would say it adds emphasis to legato-style playing so that the performer glues or holds the notes in-between -- akin to using multiple voicing to notate precise over-lapping of notes in a simpler way, though this may be completely off the mark.

{syntaxhighlighter SPEC}Chordially{/syntaxhighlighter}