It appears my original comment got hijacked then removed. In summary, I contend that ADA stake pool is not eligible for delegation because the operator of the pool is known to operate many pools and the delegation methodology says they will only delegate to single pools.
I do not remember the exact wording, but in the delegation application there was a question on whether the applicant operated more than one pool. I imagine the operator of ADA pool answered yes to this question.
CF’s position is, although the owner operates many pools, because none of the pools share common marketing each of the pools this person operates are single pools.
It was my mistake for not knowing this already after @Cardano-Foundation delegated to the 1PCT cluster. 1PCT marketed their EPIC pool outside of the 1PCT brand so it was eligible for delegation.