^ I checked online and WS is the fully-synthetic, "lifetime fluid" that toyota has been pushing. Part number is 08886-02305.
LSB was also complaining about this on his Vios also because any self respecting car guy will not feel at ease without changing his ATF during the times he feels it should be changed (or as specified). I myself had a not-so-great experience with a BMW E36 before when i was told by the SA at BMW that there was no need to change the ATF; "lifetime" daw. A few months later, the tranny failed and a post mortem showed that there was some water contamination; something an ATF flush could have saved.
From what i gather, the press release is that WS is not similar in spec to the mineral based T-IV. However, some owners using a Toyota Tundra in the US have switched to another oil and so far reported that their transmissions were running fine. Whether we would try it or not, I will have to experience it firsthand with another car before doing the plunge on mine. One thing to consider though is that given that the Gen 10 Altis is a 4-speed and is using the ZZ engine similar to the 9th Gen Corolla, i'm thinking that the T-IV transmission fluid is still compatible.
If you confirm though that the WS is what's used in your car, and your car is driven normally with no towing or carrying of heavy loads, and it doesn't ford deep floods, then you can consider extending your ATF drain interval (i.e. instead of draining at 40,000kms, change it at 80,000kms). Then you change using the Toyota WS. Even if you pay more, at least the intervals are longer.
Here are some tidbits that can probably help since it shows the transmission codes and you can try to match it up with the one on your Altis: (from
G6 Automobile - Products & Equipments)