Word for manufacturers intentionally making their cheaper products inferior even though they use the same hardware?

The practice is often called crippling (which has the usual meaning of the word: "to deprive of capability for service or of strength, efficiency, or wholeness" Webster.

The practice is also commonly used for trial versions of software. Features and capabilities are curtailed until you buy it. Then the full features are enabled.

For hardware, it can be less expensive to use essentially the same design than to develop a new version, especially if the parts cost is low and they can manufacture in greater volume. They degrade the performance, otherwise there would be no reason to buy the expensive version.

In the context you use as an example, it's called "binning"

There's no such thing as "the exact same chip" once you move to the extreme boundary of production capability. As the manufacturing process is stretched to its limit, even the smallest variations become relevant. Thus, every chip has relevant variations, and a post-production measurement tells the manufacturer how good the product actually is.

Now it turns out that separating the resulting chips in two bins "working" and "defect" is economically unsound. Adding a third bin "works, but with reduced performance" turns out to be an economical option, and for high-volume products even more bins are sensible.