External brick wall has horizontal cracks around the house (

BUT... the black vapour barrier under the slab is required to be brought up the face of the slab and terminate at finish ground level. Ask your builder how he intends to address this? as you will get water drawn by acpillary acting through the slab edge face into the slab.
The spark arrester covers need to be removed so your weepholes work.
And your gaps around the windows appear to be greater than the 2mm allowed for bushfire construction

The DCP sits under the bottom plate of the frame, the first 2 rows of bricks start at the bottom of the rebate in the slab, the DCP runs under the frame over the cavity with slight fall to the top of the second row of bricks

You have a number of issues being addressed at this location.
Bricks absorb moisture (rain), the rain moisture rundowns the inside of the brick work and drains out of the cavity at the weepholes.
The Cavity (gap) between the inside face of the brick and the outside face of the frame with paper over the top provides separation in the wall to prevent moisture bridging over to the frame.
Quite often the slab edge will be totally backfilled so that only the bricks are visible coming out of the ground. Bricks suck up water so if they are incontact with the ground they will draw water up through the bricks. The DPC stops the upward movement of the water.
The Moisture barrier sits on top of the ground (Pad) but under the Slab, its purpose is to stop water being drawn up through the ground and through the slab. Think of a tarp or anything, laid on the ground and the next day even without rain the underside is wet this is ground moisture.
The moisture barrier is required to continue out from under the slab and up the face of the slab to stop water being drawn into the slab creating a wet edge. THIS water doesn't care about the DCP as it is being drawn through the slab in all directions.
Hope this helps

Sort of but not that simple...sorry
The BCA has what we refer to as DTS systems, like a recipe. You follow the recipe exactly you are all good. But the BCA also allows for smart thinking methods. Performance Based Solutions (PBS) this is where you can come up with new ways of doing stuff. The requirement is, that to use a PBS you must document a system that clearly shows it meets the minimum standard or betters it, set by the standard recipe.
The issue is YOUR home insurance is only valid if the original built element is compliant with the BCA or an accepted PBS, otherwise your insurer will deny the claim as illegal work. (Your carpet gets mouldy and rotts and the plaster draws moisture up the wall..not covered).
Most builders will simply waterproof the slab edge, but this doesn't meet the Performance Requirements of the BCA and is therefore non-compliant.

Nice rabbit hole you've gone down!

The BCA states the vapour barrier shall be continuous. If you have a join (allowed) it must be a 200mm and taped. As the vapour barrier would have been cut back around 50mm outside the slab edge you would need to undermine the slab edge to lap and tape the join. So, simply waterproof the edge. No waterproofing product will stick to the vapour barrier (plastic).
Oh and your solution must show it can last >20yrs.

Hi, thank you all for commenting, look like I found the right one to talk to here.
@buildingandlegal: I already mentioned the crack to my builder and they said that they will talk to the brickies to investigate. in saying that it is normal and no need to concern, should I ask the builder to patch/fill/fix... that in some sort? Just because hair line crack in total of about 6-7m around the house does not look very good.
And do you do inspection service in Victoria? I really wish to have you look over my house, thanks

If the "crack" is due to DPC nothing you can do about it. Mine was also like this. It's common sense you put a thin layer of plastic between brick and mortar that's what you get.