If they are talking about a square edged entry like the AE pistons they are talking out of their behinds ....... on this planet we call Earth the laws of fluid dynamics are clearly defined .....
If your talking about comparing a bell mouthed entry to that of a square edged entry then there will be a difference, and what is more that difference will change as piston speeds change. The square edge piston will feel like it's gaining "pack" at lower piston speeds, this is to do with the transission between turbulent and laminar flow as the fluid goes through the holes.