Yes, the "as" muddles things up quite a bit, and yet it does have a logical operation in:  A is to B 
as C is to D.
Do I have the truth table of "if" right?  I looked up sentential logic on wiki and it didn't really cover that.
I think the truthfulness of 
Though depends more on the agent, and 
If depends more on the patient.
Put another way, I think "as if" is to behave according to the appearance, while "as though" is to behave according to inherence.  
I'm not sure if that's even a real word.
Ah.  
2. Philosophy. the relation of an attribute to its subject. 
(sorry about the gratuitous editing.)