I am helping in screening the admission materials. Some of the official transcripts were signed by the same guy who sealed the envelope, while others are not. Nobody seems to care about this issue, and I wonder if it is a common practice.
Generally, the transcript itself will be signed by someone with a title like Registrar, at least in the United States. The signature on the envelope will be that of the university employee who mailed the transcript. Sometimes, maybe even often, the signatures will not match, and that is likely OK.
If you are concerned about a particular case, contact the university that sent the transcript. They can tell you who is allowed to sign the envelope, and may even provide a facsimile signature via email.