Although I kind of share your anger at giving weird names to stuff that's been there for decades[0], port knocking could be considered as just one specific case of this pattern and not the general case.

What if we don't use different ports? Your example uses ICMP packages with different sizes, not ports. What if you use something at the application layer that doesn't require ports, maybe a sequence of (invalid) calls to separate end-points?

Personally, I don't care how it's called as long as everyone agrees on what it is and here, again, I agree with you in that "Gothic Hotel" might not be the best name.

[0] Just the other day I heard a plain-old FTP server described as "cloud-based storage service".