> Also I assume radar-proof is just because it's a ground effect vehicle that will never fly high enough to show up on radar it certainly doesn't look all angular like a stealth bomber. In which case my bicycle is also radar-proof?

From the way the article is worded, it does seem the author is only considering air search radar with this claim. Without low observability features, this will show up on surface search and surveillance radars. There might be an initial period where some radars fail to register it because they reject it as a possible target due to its kinematics. If craft like this become common, though, the signal processing algorithms will be updated to handle them. Most can already deal with very low-flying helicopters anyway.

That said, just because it isn't angular doesn't mean it doesn't have low observability features. Radar absorbing material would still make it harder to detect. So would more subtle elements of the physical design. I don't think "radar-proof" in that section header is justified, though.