Dual Inline Package and Chip
Often the  die cavities can be selected, based on the aspect ratio (length and width of the silicon chip) and the silicon area.
You want to nearly FILL the cavity, for good heat removal, since most of the heat (at least for plastic) has to flow FROM the silicon THRU the plastic and then TO THE LEADFRAME.
Thus for plastic, a small die in a large cavity is BAD THERMAL DESIGN.
The black epoxy has 200X the thermal resistance of silicon and copper(the lead frame often is alloy of steel and copper).
And those gold bond wires are about 10,000 ° C  per watt, per milliMeter of wire.