Nah, just because he is big it doesn't mean he is more durable. He is still a human, who is using an advanced version of transformation technique. You literally have nothing to prove this.
I'm going to address this once, and one time only because this should be common sense and something I shouldn't have to explain. This is not at all a transformation technique, again common sense. As Chouji increases in size, so does his
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. Meaning, his whole entire body actually grows in proportion to his size; including bones, fat, muscle, etc. He absolutely becomes more durable because everything grows significantly bigger. Larger muscle=
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Larger fat=
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. And the same holds true with larger bones and thicker skin as well. Again, it's common sense.