https://www.cnet.com/news/thanks-to-samsung-and-verizon-5g-is-about-to-all-get-up-in-your-face/

Samsung's exact US launch date is unconfirmed, but the S10 5G is rumored to go on preorder sale April 18, with a May 16 launch. It'll come exclusively to Verizon before heading to AT&T, Sprint and T-Mobile. 

Neither Samsung nor Verizon immediately responded to a request for comment on my theory.