I've been on the route both eastbound and westbound. Today as I write this, SQ 21 (EWR-SIN) is just reaching India, travelling eastbound. 12 hrs ago, SQ23 (JFK-SIN) travelled westbound. 12 hrs earlier again SQ 21 was eastbound. 2 days ago SQ 21 was westbound. i.e. it varies a lot.

IIRC, before Russia airspace avoidance it used to do a polar route often, and very rare to see westbound. I suspect that airspace avoidance means that it travels westbound now when it would have travelled on the polar route previously.

The outbound routes from SIN, SQ22 & 24, seem to travel consistently travel eastbound (shorter and to take advantage of "winds") , although pre-closure I think it occassionally did polar route also.