I'm going to add a "Fourth" to Sirius' list: a properly exposed and developed Delta 3200 negative may actually appear visually to be "thinner" than a properly exposed and developed negative of another type.
When your shadow detail isn't the most important part of the image, your negatives can appear quite "thin" and still print beautifully.
The following example is from a negative that looks to be really "thin". It isn't on anything like Delta 3200, but due to the nature of the light and the subject, it prints really well:
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