In HV Mode the engine will run and stop as necessary. As determined by programmers.
Low power demand, for example, may result in the engine shutting down for a brief period. On flat or down grades at 70mph. When HV is first selected it would switch to EV. ICE shuts off. After about .2 of a mile on EV the ICE would come on and then operate to either EDM only , EDM plus charging, or hybrid with battery assist. It sealed to try to hold or slowly charge back up to the SOC at the time I selected HV
Operating more like a battery hold feature that allows for plus or minus of the battery SOC when the driver had selected HV.
You may see EV Mode displayed. More power or a need to maintain battery SOC will result in the engine running. There isn’t a way to control the engine in HV mode. Timing for when the driver selects HV along routes can determine what initially happens.
In HV Mode, by definition, the car behaves as a Hybrid, using both gas and electricity. Sometimes EV only. I would had preferred to leave the ICE operating when I select HV. Let it keep running, oil temps stay up, and less shut down start up. If ICE energy isn’t needed, let it slowly charge up the battery. I believe this is how the first Honda plug in hybrid worked.
Engine Drive Mode (clutch engaged) will only operate at speeds above 45mph. It will disengage under moderate acceleration. It has reportedly remained engaged up to 85mph. Yes, the car seamed to stay in EDM at higher speeds without disengaging as frequently as 70mph.
Some folks have reported success in forcing EDM to engage by switching from HV, to EV and back to HV. I’ve had moderate success getting it to engage by easing off the accelerator until just a touch of regen shows, and then easing back on the accelerator. It will disengage when the vehicle is operated outside of the speed and torque parameters which need to be met in order for it to engage.