I can answer that, NO! I tried that yesterday and Boost would not activate it. It was an unlocked sprint branded s8+ but because It wasn't sold by Boost they won't activate.
The point I was making is that they will only activate a phone bought from them. If you go and buy the same phone from Best Buy they will not activate it even though it's able to function on their Network. Best Buy is now looking into the issue because they were surprised that the phones that they have been advertising as working on the Boost network are now being refused activation by Boost.
If I want a new high-end phone without having to order and wait for shipping then I have to go to a different carrier because boost doesn't sell high-end phones in their stores.
I got my phone from Best Buy on launch day and took it to a Boost store once they listed it as usable from Sprint no problems at all. So no idea where your getting your info from.
Not sure if this will help but did you buy a Boost Sim Card kit? I purchased a S9+ (not from Boost plus a Boost Sim Card kit from Best Buy) and got my phone working on Boost. So you don't have to buy a phone from them to have it working on the Boost network.
