British and Japanese night doctrine grew from experience as well as alliance

Did the Anglo-Japanese alliance explain why both navies emphasized night fighting?

It may have contributed, but World War I combat and each navy's later operational experience were also important.

The question notes that the Royal Navy and Imperial Japanese Navy became especially associated with night fighting and asks whether their alliance explains the similarity. The alliance was one possible influence, alongside World War I combat and each service's later operational experience. Both navies worked through night tactics in their own circumstances. Doctrinal resemblance alone does not show that one navy simply copied the other.