Tour Int just did a test on their flat rig
https://www.tour-magazin.de/magazin/aktuelles_heft.html

They stole my money once, so I was comfortable posting their articles for a while. Now I feel we're even after continued solid content. So I won't.
They tested:
Cont Terra Speed, Terra Trail
Kendra Alluvium Pro Boost Pro
Pirelli Cinturato Gravel H, M
Schwalbe AllAround, Bite
Vittoria Zero, Dry
WTB Byway Venture

40c tires 30kmh w/ 90kg pair on flat rig over stone and tarmac 2 bar (30psi) , 3bar, and 4bar (60psi)

Key takeaways: g-One Allaround performed the same as the Cont Terra speed. WTB still roll like ****. 30psi makes 4w difference on the road here. 60psi top level gravel tire takes 23.3w on this rig, a 7bar top level road tires does about 18.4w