C doesn't even originally have true/false, I think you may be conflating the two concepts that "any nonzero int is truthy" and "boolean expressions evaluate to ints". The standard mandates that boolean expressions like equality always evaluate to 0/1.

The `true` constant is always 1. C11 §7.18 (3):

> true which expands to the integer constant 1,

And equality yields a 1 or 0. C11 §6.5.9 (3):

> The == (equal to) and != (not equal to) operators are analogous to the relational operators except for their lower precedence. Each of the operators yields 1 if the specified relation is true and 0 if it is false.