How did H. erectus reach Flores 700k to 1 million years ago? In the last million years the earth has had 7 or 8 glacial cycles with sea levels changing by as much as 400 feet. So the question regarding travel includes how close were the larger land masses to Flores during the periods when the sea level was 400 years lower than it is today?
Regarding crossing the Mediterranean at Gibralter I have another question. How many times when the sea level fell too low to enter through the Gibralter area did parts of the Mediterranean dry up as a salt flat? How many times and in how many places could Homos have walked across from Africa to Europe in those times? When and where was the most recent period when land transport from Africa to Europe or reverse possible?
Flores hasn’t been connected to the mainland, even during those glaciations.
Oh, regarding the Med, the last re-inundation (ending the “Messinian salinity crisis”) was over five million years ago.