Given that the ranking is already based on top-tier conference publications in each field, isn't the author introducing their own subjectivity by excluding professors based on their current university affiliations? It seems quite easy to adjust for EE departments that are obviously prolific in CS fields (as defined by the conferences counted in those fields).
I think the problem is kind of opposite of what you are saying: why should the history or bureaucracy of each university take precedence over the publication metrics when everyone seems to agree that fields like embedded systems and computer architecture are part of "computer science"?
Shouldn't the purpose be to help prospective graduate students evaluate the strength of PhD programs in the fields they are interested in?
I think that excluding research in companies or universities without PhD programs is much different than excluding EE/ECE professors who happen to be at universities where the bureaucracy makes it difficult for them to have some sort of "official" appointment in the CS department. It is also much more rare that these entities publish in the top-tier conferences that csrankings counts.
Note that it is not just professors who can advise CS PhD students, it is professors who can SOLELY advise a student for a CS degree. It would help even if EE professors who have co-advised CS PhDs at the same university were allowed to be included.
I think the problem is kind of opposite of what you are saying: why should the history or bureaucracy of each university take precedence over the publication metrics when everyone seems to agree that fields like embedded systems and computer architecture are part of "computer science"?