Hi, and welcome to psych central! IMO, the T will want you to share about "today" for a few reasons: to help create a foundation of trust for you to build upon, to allow T to see how the past could be affecting you in your "today" life, and also to note how you speak regularly, how normal talk flows (or doesn't) and generally get to know you... so they can tell the difference once you get into those "childhood" issues.

I agree, an open discussion where you ask the T why this is necessary, would be a good topic!