Yes, it seems like abundance of caution to me. If driver has become accustomed to regen being there as a part of the braking, it will take a moment for driver to realize to push harder on the brake pedal, or move foot the the brake pedal for a driver with the habit of one-foot driving.
I appreciate JLR doing this instead of having a feature where if it doesn't work and the car runs into an object, under objects, or over people resulting in damage, injuries and deaths, they'd just blame the driver for not being attentive, insufficient reflexes, or foolishly using the feature as it has been touted to work (although it wasn't guaranteed to work in all situations). "Model T" come to mind, anyone?