I'm pretty sure that's not correct. You definitely need Mobile Priority to operate in the black patches, e.g. at sea. But there are two ways to get Mobile Priority. One way is to sign up outright for a Mobile Priority plan ($250/mo, 50GB included). But there is another way as well. From a regular Mobile plan, you can Opt-in/out of Mobile Priority, paying $2/GB extra when on Mobile Priority. When you opt-out, it goes back to being regular Mobile which is unlimited data, blue patches only, and best-effort speed/priority. This later is what I have been using, and I opted-in for a stretch of black patches, but have otherwise been opted-out.
As for in-motion, I guess it's one case where the policy and enforcement are different. 95% of my cruising has been on regular Mobile and it has worked all the time while underway, no hate mail, etc.
Now I DO have the Flat High Performance dish, which I understand to be the ONLY dish that is formally supported for in-motion use. But again, it's clear that in-motion use with the other dishes is not blocked or warned against via hate mail, except when it is.
I was on the RV Roam plan with the toggle for Mobile Priority set to on when I left Gray's harbor. As soon as I got offshore, SL told me I had to upgrade to the plan called Mobile Priority, and they apparently weren't kidding as I lost connectivity.
Whatever, it's worth pointing out that the boffins at SL haven't bothered to update their website to match what their service plans actually offer. You can only find that out on their app. In brief, here is what their app says, and gosh darn if this isn't how it works for me, assuming you can define what they mean when they say "ocean":
"Mobile Priority - 50 gb. $250/mo. Use Starlink
on the ocean or land across the globe..." Delfin note: The plan I am on.
"Standard - $120.00/mo. Standard service for residential customers
at one location."
"Mobile - Regional - $150.00/mo. Use Starlink at any location
on land in your continent.....
not permitted for use on the ocean. Metered Mobile Priority data high speed ocean access, can be purchased by the GB on this plan." Delfin note: The plan I was on, with mobile priority data on and ocean access was not available outside 15 miles or so. I know because my access was turned off at that point. So yes, you can be on the "ocean", just not, like way out in the ocean. I guess.
"Mobile - Global $200.00/mo. Use Starlink at any location
on land across the globe.....
not permitted for use on the ocean. Metered Mobile Priority data (for) ocean access, can be purchased by the GB." Delfin note: Maybe, but I suspect that like "Mobile - Regional", it won't work in the deep blue.
Since my realtime experience seems to differ from the experts on the thread, I'll defer to them.