So far this hasn't been shown even on much simpler Falcons. The barge gives quite some energy advantage for not having to boost back.
Ideally they'd build a capesize kinda barge with chopsticks to catch it in the ocean, then perhaps service what they have to while it's steaming back.
SpaceX did purchase some oil rigs with the intention to turn them into launch platforms, but later abandoned the idea. It's probably something they will return to later once Starship is flying regularly. You're right that avoiding the boostback burn is a big advantage. But maybe they don't need to bring the booster back after it lands on a platform, it can just launch again from there. Maybe they could have a bucket brigade of launch platforms ringing the Earth!
I.e. the bulk of near / intermediate term launches
Far fewer people care if you "oops" an unmanned rig in the ocean.
You have to get fuel, and the rocket, out to a pad in the ocean, and have to deal with a rocket lift on varying conditions.
If you dont want to do most of that, then the only option is putting your manufacturing on the rig too, which negates lifting a rocket, but instead makes the rig huge, and requires having a train of ships in and out 24/7 to keep it supplied.
There was even a company in the late 90s that tried oil rig launch platforms and ultimately abandoned it.
Since the 2 stages of Starship aren't intended to be road mobile, due to size, there's no transportation benefit to being land-accessible.
So really the main concern is piping propellant... but afaik some rigs off the shallow coast of Texas are directly piped to land?
The main benefit you get is terrifying the FAA et al. less, as the consequences of a missed catch are now out in the ocean.
The fact that it's required for Artemis to work, and the amount (nobody knows exactly but lower bound is like 15) of Starships required to launch in quick succession just highlights how risky, to the point of unsoundness, the project is.
If you do the thermal design right, possibly use a sun shade (space is a large thermos bottle after all) or even use active cooling to remove the little heat that gets through, then it should work just fine. :)
Spaceship and/or super heavy are (I don't remember the details).
Then the ULA CEO Tory Bruno claiming that the SpaceX photos of the first Raptor 3 were “partially assembled”, to which Gwynne Shotwell replied with this: https://x.com/Gwynne_Shotwell/status/1821674726885924923?t=v...
And yeah, Starlink was a great purchase by SpaceX.
So, while engines without tilting have been used - e.g. NK-15 - Raptors aren't from that category.
There's clearly a huge advantage somewhere.
Not necessary for launch.