Currently, PowerPoints "open arrow" ("----->") gets imported as LibreOffice's "line arrow" ("----- >") with a gap between the corner of the ">" and the "---".
Expected: The "----" connects to the corner of the ">". That's what LO's "short line arrow" does.
Cf. the different arrow types at attachment 130946 [details].
The issue that LO's "short line arrow" looks like "====->" (thiner arrow head) is bug 105796.
Created attachment 130947 [details]
PPTX file (PowerPoint 2007) with the different arrow heads
(Side remark: the MS's "stealth arrow" maps to LO's "arrow concave" which has a similar gap issue.)
Thanks for reporting the bug.
It seems like a duplicate of bug 82760
*** This bug has been marked as a duplicate of bug 82760 ***