Confirmed

Interestingly the result vary depending on the direction (the side of the target you attack):
Front and Back gives you the craters with peaks as described in the report.

Impact on the side (along the x axis) gives you damage along a line, attack from left leaves a damage line below the impact point and on the right side that damage appears above the impact point.

impact on the ventral or dorsal areas gives a different structure

those structure also appear when attacking an unshielded target (in addition to the expected crater)

Addendum: This behaviour make missiles extremely weak against shielded target when attacking a flat side area, as you need some minimum damage per missile to have those structures appear (below a certain threshold every missile just kills the shields and does not damage the structure/armor)

sounds correct to me.
the damage expands as a sphere and if the damage gets blocked by a shield (even though it kills the shield) it wont expand further in that direction. and depending on the impact angle there are different shapes of the effect to be expected i guess.

just from the description here without testing it myself i wouldnt consider this a bug.

In T494#16939, @SmilingDemon wrote:

sounds correct to me.
the damage expands as a sphere and if the damage gets blocked by a shield (even though it kills the shield) it wont expand further in that direction. and depending on the impact angle there are different shapes of the effect to be expected i guess.
just from the description here without testing it myself i wouldnt consider this a bug.

I would agree if this were not so completely different on the sides -> please note the last line of my comment