if (expression) VS "Traditional If" in AHK

The following simple script displays Yes, then No.

I don't get it.

From what I read in the AHK documentation, I suspect this has something to do with the if (expression) VS "Traditional If". But I find the documentation not very clear on this subject.

Could someone explain this?

#SingleInstance force
#NoEnv

Toto := "c"

If (Toto In a,b)
    MsgBox Yes
Else
    MsgBox No

If Toto In a,b
    MsgBox Yes
Else
    MsgBox No