The additional S was on purpose to check hidden option.
If you deliberately change it, why iGP should change "back" to the tyres of 4th option. It doesn't make sense to me.
Strategy 18 I 16 I 16 I 13 and an additional S
I still don't understand why you put 13 laps on last stint, it would require a 5th stint even in normal conditions.
... before he was waiting 0mm before change..
When I mention it waits to put S in 0.0mm water is because the dry tyre is in the MAIN strategy.
ok, so Villeneuve did his "if stops raining" straight way in the last stint because the AI thought it would be the best option. The AI can't recognise it's a dry tyre in that option and therefore it should wait more laps.