My understanding is that braking in an EV is usually brake-by-wire, and depressing the pedal will command regenerative braking up to the limit of either (what the user commands) or (what the battery/motor can handle), adding in mechanical braking only when the regenerative mode can't brake as hard as demanded, or at low velocities where regen can't generate meaningful force.
So the difference, in an EV, between "engine braking" (i.e. releasing the accelerator pedal) and "braking" (depressing the brake pedal) is that it modifies the mapping between pedal depression and commanded action, not that it actually switches between dumping kinetic energy as heat or chemical potential. If you need to dump, e.g., 100kJ of kinetic energy, you're still going to recover (example numbers only) 60kJ into the battery and 40kJ into heat, regardless of whether you do that by releasing the accelerator pedal with light regenerative braking, heavy regenerative braking, or by pressing the brake pedal down.
Well, unless you are in the habit of braking very late and hard so that you perennially overload whatever limit the motor/battery an handle and thus rely on more mechanical braking than necessary.