It turns out that the operating system on the new iPad Pro limits all third-party apps to a maximum of ~5 GB RAM each.
Such an odd limit, and perhaps one that will be removed at WWDC in under two week’s time.
The iPad is primarily intended as a single app workspace, considering how complicated and undiscoverable the multitasking features are. Why restrict that single app you have open from consuming more than 5GB of RAM?
Unless there’s some surprise multitask features in the cards for WWDC?