It wouldn't have changed in 2020 as the transitional agreement meant that all the former rules continued to apply. The 2021 figures will be more significant.
I suspect that because Singapore is a regional shipping/trading/commercial hub many British goods exported to Singapore ultimately do end up in India just via Singapore. Those goods statistically then count as exports from Singapore to India even though they are only the intermediary.
Japan has very little natural resources, so no materials, and pretty much no food. Technology would be the main import I suppose, but that's definitely not more than any other countries.
Nice quiz