Ответ на этот вопрос должен разъяснить очень важную разницу в буржуазно-демократической и социал-демократической постановке вопроса о религии.
The answer to this question will serve to explain the very important difference in the way the question of religion is presented by the bourgeois democrats and the Social-Democrats.
I think you are right that by 1920s that term was mostly associated with Mensheviks but I swear I’ve seen bolshevik references to it even in 1910s, so it wasn’t as clearly defined as it is now.
I swear I’ve seen his post-split works still referring to his movement as social-democrats.
Found it (1906): https://ru.wikisource.org/wiki/Социализм_и_религия_(Ленин)
I think you are right that by 1920s that term was mostly associated with Mensheviks but I swear I’ve seen bolshevik references to it even in 1910s, so it wasn’t as clearly defined as it is now.