Not necessarily. For all reasonable articles of clothing, yes, it's true. That's because clothing is designed to enclose an interior which is isomorphic to a sphere [1]. Thus, clothing is simply a sphere with holes.

But there are plenty of hypothetical clothes for which this isn't true. Consider a mobius strip - like a sack, there is only one hole, but a mobius strip isn't a sack (and you can't patch it shut).

[1] I don't want to think about clothing for which this isn't the case, since it would involve the digestive tract.