Why do they place a high current device in a low current package?
The link you had goes to a supplier, who, it appears, doesn't read the data sheet very carefully. I would argue that they should be listing these exact parts at the lower current in the packaging provided.

The internal silicon is capable of higher currents, but the data sheet clearly shows that, as packaged, these parts are not capable of such high currents. Refer to figure 9 on page 5 of the data sheet:



They could manufacture a 75A silicon part just for these packages, but that would result in significant part proliferation and stocking issues.  As it is, they manufacture the one part, store it as dice for a short time, and package it according to customer demand.  This reduces the load on their plants and storage facilities, and they can focus on improving the reliability and lowering the defect rate of one part rather than two, or more, different parts.