The first "small" agent is needed for the software distribution action, thats the reason why only the software distribution components are selected. And as I wrote above the policy sync has to be in the far future because it can interrupt your provisioning template if you leave it default!
At the end, the main agent is installed because normally the policy sync should run daily or hourly not in the far future...:-)
Thats the reason why we work with two agents and its recommended by LANDesk support too.
Hope it helps.