Looking for advice from weed experts

That is Buffalo you are pulling out. It comes out easy because it only has surface runners called Stolons. It does not have thick subsurface runners called Rhizomes. Your lawn needs water and most likely a Liquid wetting agent. It looks like Hydrophobic soil to me.

liquid no survive Adelaide summer

That’s just a different type of grass. Buffalo I think. Grows like crazy

buffalo grass is very good for SA, as it's quite drought resistant, but isn't very good if you just want to weed spray everything. Hence lazy people calling it a weed

You need to let the bud mature a bit more, should end up with a formation like pic related after a few weeks more of growing.

a winks as good as a nod to a blind bat

The thicker grass is buffalo. Your choice as to what you prefer. If the "normal grass" is a couch, you'll never kill it.

People spend $12 a slab for buffalo grass at Bunnings. Compared to cooch It's technically a thicker and, when established, makes it hard for weeds to establish. In saying they it's weak to most selective herbicides that normal grass can handle.

It is Buffalo. It ain't kikuyu. Personally I would let it take over. Cut it slightly longer than your current lawn. It is easy to remove from unwanted areas when the runners go wild.