The main toolbar contains separate icons for 'Lines and Arrows' and
'Connectors'. This suggests that these are in fact two separate types of objects
with individual attributes (which should translate into individual styles).
However, editing the style for connectors does in fact edit the style for lines,
e.g. if I choose a different linewidth for connectors, then this new line width
is also applied to normal lines which are not connectors. Also, changing the
arrow style for a connector does not have any effect on the connector at all but
changes the arrow style of lines (I'm talking about editing the style here, not
attributes of an individual object).

From a more practical point of view, a drawing may contain both connectors and
lines. The default arrow style of the connectors may not be suitable.
The only way to change the arrow style of the connectors is to do it one by one
for each individual connector in the drawing. Being able to change the default
arrow style independently of the the line style would be very helpful in this
scenario. This is what one would expaect from the styles concept in the first place.

[I think from a user's point of view this qualifies as DEFECT - I'm a user so I
must know, right? ;-) I acknowledge, though, that from a developer's point of
view this might be more in the FEATURE REQUEST category - I have no idea how
this is handled internally in OpenOffice.]