One of the meanings of “baroque” is “Extravagant, complex, or bizarre, especially in ornamentation”, or so DuckDuckGo tells me: https://duckduckgo.com/?q=define+baroque. Also see: https://www.cs.utexas.edu/~EWD/transcriptions/EWD03xx/EWD340....

And it's pretty clear that McIlroy used “efflorescence” as a metaphor for “proliferation (of features)”. This usage of “bloom” and its synonyms isn't uncommon.