I looked at them and they just look like presto logs in a brick form. I’m not sure why they would burn differently. Maybe they can be packed in tighter and this restricts the airflow better.
That's exactly correct. I too was nervous at first and concerned about a runaway fire. But if one follows their instructions, they burn as advertised. The secret is stacking them so that air can't go easily between the bricks. Then they burn slowly as a mass and work pretty well.
Thanks for the tip about the Atlas bricks, I'll watch out for them.