What I hadn't quite fully appreciated was the fact that there's 2 modes of incall.
The first being very simply walking in.
The second being a network of off-site locations, mostly apartments near the Hub, where girls may be working from.
I guess that expands from the a few (?) rooms available at the walk-in site, to more offerings. Downside being if logistics needs to be worked ahead of time (e.g., for parking reasons, or if working to a tight time window) then the off-site options would be left to a late decision. So even though the Rota is published, it's not clear where each of the girls may be ...
... at least that my attempt at joining the dots. Likely similar story at affiliate joints.