I know, I know, slow ol' me, but what's the problem with an Allied bomber, or more particularly a Nederlands bomber, being off south Borneo on February 17, 1942? The coordinates given would put Yubari Maru
likely heading either into or out of Ban(d)jarmasin, across the Java Sea and NNE of the MLD base at Soerabaja. Now you make much of the spatial dilemma, aber nicht the temporal consideration. What would have stopped a Dornier Do-24, with a combat RADIUS of 2900 km (1566 nautical miles), armed with a dozen 50 kg bombs or half that number of 100 or 120 kg bombs--perhaps the beneficiary of previous naval intelligence or just stumbling onto this small enemy merchantman while on a routine patrol--being over this spot of the Java Sea during either period of crepuscular light--i.e., dawn or dusk--on this date? What would have stopped this hypothetical* armed flying boat, crewed by a buncha sharp-eyed young stalwarts infused with derring-do, from putting this luckless Maru under the waves?
*I write "hypothetical" because the Hyperwar site doth qualify the PROBABLE cause of destruction as Dutch aircraft.