Do grate heaters without blower work?

Looking at relatively inexpensive ways to have prefab fireplace actually being a heat source. Right now it barely gives any warmth to the room, it all goes into the chimney. Do those hollow tube grate heaters actually do anything without a blower installed or it’s all marketing? Talking about units like this https://www.fireplacedoorsonline.com/5-tube-fireplace-grate-heater-for-zero-clearance-fireplaces.html

Thank you!