As I'm testing IBY from the client side, I find that the Products section doesn't feel right in that it shows you products from the selected session. I think my discomfort stems from the belief that the client probably doesn't realize the products will change in that section depending on session type. Other carts I've used have had a standalone section where universal things like sitting fees, brand swag, frames, etc. could be sold that don't necessarily apply to a specific gallery. I think the section could function almost like an infomercial area.

Consider the not-so-edge case that a client just logs into his or her account but has not yet selected a session - what are you going to show in the Products tab? Maybe the best solution i is a product flag to identify products as ~"universal - show to all sessions, client types, etc." (this would be something like gift cards), ~"session type specific" (this would be something like sublimated photo dog tags for someone who does pet photography), etc. Maybe based on Session Type you can also hide universal products. IDK. But really, I don't think Home upon login should default to a session, and I don't think you should default product offerings in Product section without a client making a choice of a session to make the products relevant.

End analysis: make Products section show universal-tagged items by default. Add flag for session-type-specific products to show in Products section when a session of that type is selected. Make it possible for universal-type products to be hidden for a certain session type.