I bought an F ticket for SIN-KUL but wasn't able to select a seat during the online booking. I'm guessing it was because I don't have a KrisFlyer account (used my United MP account). Called them this morning for a seat assignment and was told that they don't assign seats for shuttle flights, not even for F. Is that really true? Do I get a seat only when I check in at the airport?

A search came up with plenty of info on SIN-KUL standbys, lounges, alternative transport methods, but nothing on this particular matter. Thanks!