I guess you're not famillar with how huts have appeared. The cave's got some formidable fortification nowadays, the only reason for doubt about the lamp is that one modern fake, I don't think the fakery extends to everything, just that the cave hasn't been open for proper study by the look of that and the number of photos taken of the lamp. It's not a stretch to think they really did have lamps in caves.
As I said, I'd love it if it were a representation of a ship, but among antiquarians, the view is, it's a hut.
The reason seafaring is known to be at least 800K old is, Flores Island (now better known for Floriensis) has artifacts that old, and during the currently accepted time of humans/hominims the island has been divided from the mainland by some miles of open water.
antiquarians who do not want to rock their particular boats of consensus thinking - who would not know a ship from shinola. Forget what it is ‘supposed to be’ and just use your eyes to see what is there piece by piece