Thanks to OP, MOH has woken up today and will start tightening border restrictions from tomorrow, restricting those with more infectious strains from UK and South Africa. I think MOH balls dropped with unlinked community cases and scared they be blamed responsible for a second COVID wave.
s://mothership.sg/2021/01/all-travellers-sg-covid-19-test/

But why not bar India flights too with their huge cases? MOH got new CECA citizen in charge of border restrictions?