I agree there are no "throttles" per say in a jet engine, Boeing refers to "auto throttle", and Throttle hold mode is when the mechanical clutches are disengaged allowing the thrust levers to be moved by the pilot, even though the auto throttle system is active...no specific thrust setting is "held/maintained" the authrottle clutches are simply in a "null mode"
"Throttle hold" is the proper nomenclature...