I quickly looked at snipets and  by what I can tell, those  two statements should be equivalent
The order of operations  would have the not expressions be evaluated first and then the and statement

Since you are inverting the boolean expressions,  the and statement should always eval to false.
In my head I can see what sesame is really doing is this :

If NOT (False AND NOT True) Then
	WriteLn( "Why am I here?" ) 

It appears that sesame isn't following order of operations for whatever reason and is just going straight across the expression
I dusted off the sesame programming manual and it says that it evals not before and expressions

Most of these don't apply to sesame obviously but should show how the order of operations should go:
Simple Assignment Operator

    =      Simple assignment operator

Arithmetic Operators

    +      Additive operator (also used for String concatenation)
    -      Subtraction operator
    *      Multiplication operator
    /      Division operator
    %      Remainder operator

Unary Operators

    +      Unary plus operator; indicates positive value (numbers are positive without this, however)
    -      Unary minus operator; negates an expression
    ++        Increment operator; increments a value by 1
    --          Decrement operator; decrements a value by 1
    !          Logical compliment operator; inverts the value of a boolean

Equality and Relational Operators

    ==      Equal to
    !=      Not equal to
    >      Greater than
    >=      Greater than or equal to
    <      Less than
    <=      Less than or equal to

Conditional Operators

    &&      Conditional-AND
    ||      Conditional-OR
    ?:      Ternary (shorthand for if-then-else statement)

Type Comparison Operator

    instanceof      Compares an object to a specified type

Bitwise and Bit Shift Operators

    ~      Unary bitwise complement
    <<      Signed left shift
    >>      Signed right shift
    >>>      Unsigned right shift
    &      Bitwise AND
    ^      Bitwise exclusive OR
    |      Bitwise inclusive OR


as parenthesis, they should be used to make the code clearer and easier to follow, just blindly adding them when in doubt isn't a good practice to follow.