  Previous studies with first-principle-based integrated modelling suggested
that ETG turbulence may lead to an anti-GyroBohm isotope scaling in JET
high-performance hybrid H-mode scenarios. A dedicated comparison study against
higher-fidelity turbulence modelling invalidates this claim. Ion-scale
turbulence with magnetic field perturbations included, can match the power
balance fluxes within temperature gradient error margins. Multiscale
gyrokinetic simulations from two distinct codes produce no significant ETG heat
flux, demonstrating that simple rules-of-thumb are insufficient criteria for
its onset.
