Yes. In the past, some hotels have offered special packages which do not earn credit. There were many, many complaints, and I believe they may have changed it. I'm not 100% certain, since it hasn't come up lately.

Travelzoo rates have never earned credit. For a hotel to put that code on a special they emailed directly to former guests (I believe that's what they did) is patently unfair. The disclosure is in the T&C, and frankly, I'll bet not many people know that Travelzoo rates don't earn credit even if they see it.