Inconsistent ship dates for S9/S9+ pre order

[Android Central Question]

I am trying to figure out why it is so much inconsistency surrounding the ship date of the GS9/9+.I pre-ordered a GS9+ on 3/2/18 form Samsung.com. Samsung said "guaranteed delivery by 3/14" prior to pre-ordering and still does. I have spoken with several Samsung reps that have given inconsistent information. I have heard "Guaranteed ship by 3/14", "Guaranteed delivery by 3/14", "It will be delivered prior to the 14th." I had a rep today argue with me stating that "the promise is for it to be shipped out on 3/14 not delivered by 3/14" despite the site still saying "Get your phone first.order today to receive BY 3/14." Receive BY or delivery BY indicates(to me at least) that the phone will be on my doorstep BY 3/14. Meaning that 3/14 is the latest. This is my first time pre-ordering a phone as I normally go to the store after release. Any one have any experience with pre-ordering phones? Do they generally come prior to the "launch date?"