Old fashioned communications planning was all about messaging.
Customers dont do A because they think B. So if we want customers to do A we have to tell them C. The assumption was attitude preceeded behavioural change.
On other the hand if someone wants to describe digital planning they use keywords rather than what they are trying to achieve for their clients (which is odd in itself) ... information architecture ... engagement ... SEO ... content management ... social media ... HTML.
Strikes me that planning used to be about asking the question what do we say? Nowadays good planners, digital or not, ask the question what can we offer - information, added value, experience? Before they ask what can we say.
(Yes, we should all have working knowledges of HTML, social media ...)