I think the rationale behind this is that many countries will fine the airline around $10,000 for each passenger that doesn't have the right immigration documentation and has to be deported. So there is a reason they err on the side of caution for them at the expense of making your life harder
Seems like there are two problems that need to be solved before then:
1) reentry and landing - seems mostly achieved, based on the "water" landing, if you were landing on mars you would need legs so the "tower catch" isn't relevant IMO
2) orbital refueling - this seems to be where the technical uncertainty is, they need to do it for the NASA HLS part of the Artemis 3 mission anyway
If they fail at 2), neither Artemis 3 or "Starships to Mars" will happen. But if they succeed, why wouldn't they send them? Then 6-9 month later they can try and land on Mars, I personally think that the Martian atmosphere is probably much more predictable than Earth's atmosphere due to the greatly lower density,so if they get there I think they'll succeed at landing too. And that way they get enough data in time to design and build the planned crewed starships in 2028
So basically one (big) technical problem to solve - if they can launch fast enough in the next two years, I think they'll solve the refueling part within 10 launches and have enough time to make, launch and refuel 5-8 ships before the transfer window to Mars