Names will not be spelled the same. Sometimes a name can be spelled multiple ways in one document. What the researcher should look for is whether the spelling of the names are consistent with how the name probably sounds when spoken.
That concept of relative consistency applies to more than just spelling. Age, place of birth, occupation, and other characteristics of your ancestor should also be relatively consistent from one document to another.
Nothing will be 100% consistent. Do not expect it. Humans make mistakes. But records should provide information that is in general agreement with other information known about the person.
Unless they are outright lying. But that’s another problem.