My memory is that the idea is related to the smoothness of the metric/gauge terms: these should be C^2, so are sufficiently differentiable to be "best" approximated (at the second order that Whisky/GRHydro worked to) by the midpoint rule. However, if included within the fluxes then they would implicitly go through the reconstruction/Riemann solve stage, so would - in places - be limited to lower accuracy.
I would not do this now - keeping the fully densitized terms together is cleaner and a better way to extend to high order.
Ian ________________________________ From: Roland Haas rhaas@illinois.edu Sent: 31 October 2021 20:28 To: Ian Hawke I.Hawke@soton.ac.uk Cc: carpetx-developers@einsteintoolkit.org carpetx-developers@einsteintoolkit.org Subject: Re: lapse terms in Whisky's fluxes
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