Edit: kragen has good overview of this below from the generator in a puddle.
Now in practice, most small generators that you buy as a consumer are "floating neutral," which means that the generator chassis, EGC, and generator GSC (i.e. neutral) are NOT bonded together. Floating neutral generators are another, very long post.
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Source: 6 years ago, when the NEC changed substantially for small portable generators, I wrote a multi-part series on all of this for a trade magazine in the pro audio industry, who make prolific use of portable power distribution systems, and generators, in the 3kW to 500kW size range.
In the course of writing that series, I dealt directly with the EE who works for PGMA, the portable generator manufacturer's trade organization.