chronological feed nuisances can be blocked or not followed in the first place. It is absolutely not an algorithm by the definition we're all using here.

It is an algorithm on a data structure, but it is not an algorithm to drive ad impressions.

do you see the difference?

this is why people say "Algo" when talking about the latter, and "Algorithm" when talking with other like-minded people about data structures and algorithms.

Someone chose "most recent" when implementing "most recent", and then that decision automatically controls what is shown next. They could have chosen "most recently liked" or "most liked" or "minimum MD5 checksum" or "alphabetical" or "most liked in past 24h" or "likes / hours * followers / followee_ratio * poster_birthdate_days_diff(admin_birthday) * tfidf_rank_matching_books_published_in_1885" - all of those would be algorithmic sorts in my book. "Most recent" is just one (among multiple) of the simplest ones to predict the behavior of.

A fully human-curated feed would not be "algorithmic", in contrast. Print newspapers do this, and sometimes online ones to varying degrees, and most blogs. You could even let people build their own (e.g. "boost to my popular feed [at position X/newest/oldest]"). Essentially none do this though, they all choose algorithmic ones of varying complexity - it doesn't make them non-algorithmic to choose a simpler one.