Patches, definitely not. For instance, if your root drive were specified there (both SVM and VxVM require this), then wiping out changes to it would likely leave the machine in an unbootable state.
In an OS upgrade, it might notice that some settings are no longer valid and remove them. (Sometimes kernel variables change names or are removed). I don't believe that it wipes out all changes.
Does your question mean that this happened to you?
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Darren