User blog comment:RainingPain17/New GTA Online update revealed/@comment-25368842-20150603102955/@comment-25261281-20150603120358

It does appear that this Online-only DLC thing was made for PC version, so players won't start storyline anymore with free stuff in their inventory/garages (just a theory of mine though).

For your point 1, see the rest of the phrase: "and be on the lookout for another big shipment coming this summer.". I think the 'some' refers to this update's content and the rest will be released on part 2 update.