Maybe a practice auto-land without CAT3 runway protections and someone was given a conditional line-up behind him. I remember seeing this a few years ago at LGW when a 757 was doing one and a 747 lined behind just as he was in the flare. Became quite exciting for a short while! Note: The tower did warn him that there was no protections!
Unless the SIA had some sort of steering problem then it sounds plausible.