In the last line it states your exact problem.
""The Device is Unlocked would work for Local and International GSM Carriers. (AT&T T-Mobile Etc..)""
It is unlocked for local and international GSM carriers only; not CDMA like Boost/Sprint.
Just make sure the Unlocked is checked at the top its $200 less than carrier branded phones at least from Samsung directly. If you where buying from ebay or amazon I would ask the seller before purchase to make sure it is Samsung factory unlocked not carrier unlocked.
I purchased mine that is on Boost right from them with the rebates I got for pre-oder from my work and my old S8+ I pad less than $500 total.
The Boost Mobile reps have the same information we do they won't know about any availability until it's already made public and you can find it yourself. Last year before they offered the LG G6 I kept asking if it was compatible and they kept telling me no but yet I was able to buy an unlocked G6 and have it connected. So if you really want to know or find out you need to go through that BYOB and just try it.