Interesting. I was departing 30 mins later. After much confusion from ground control on taxi out as to where everyone was, we had a 40 min hold for release time. We sat short 18L monitoring tower and shooting the breeze. Let me set it all up.
1) 18r is preferred departures in AUS in the am. No CL lights, so 1000rvr. All aircraft (well most) were requesting 18L, and ground seemed agitated.
2) There is no ground surveillance, so ground was often forgetting where each plane was. (Shocked in adsb age, there’s no low cost solution the could budget for.
3) due single runway and no ground radar, line-up-wait not utilized.
4) tower, at this time, seemed to be giving extra large spacing between departing and landing traffic. Like 10 miles. (Now I know why)
I commented on this to my FO, and said this could get messy if they tighten up arrivals/departures and someone rejected or misunderstood the immediate to clearance. I’m single rw ops, our expectation bias is line up and wait. Don’t know what took the Southwest so long as they always seem in a rush. Perhaps when he called ready, they weren’t quite, or even near the hold bars yet. Seems common for them to call ready 100m away from holding point. Tower would have no idea that they weren’t quite there yet.