Standardized by JEDEC earlier this year as JESD323, CUDIMMs tweak the traditional unbuffered DIMM by adding a clock driver (CKD) to the DIMM itself, with the tiny IC responsible for regenerating the clock signal driving the actual memory chips. By generating a clean clock locally on the DIMM (rather than directly using the clock from the CPU, as is the case today), CUDIMMs are designed to offer improved stability and reliability at high memory speeds, combating the electrical issues that would otherwise cause reliability issues at faster memory speeds. In other words, adding a clock driver is the key to keeping DDR5 operating reliably at high clockspeeds.
Marketing promises effectively constitute a binding unilateral offer, for the purposes of contract law. When a customer signs up, you also have acceptance, consideration, and intention, thus forming a valid contract. Carlill v Carbolic Smoke Ball Company is the classic case in English contract law; the principles are basically the same in the US.