The simple answer to this is yes
For a long time it was a major selling point for anti-virus products to recognize the signature of more viruses than their competitors.
The achieve this it was common practice for internal engineers to create variations of actual viruses, which could then be added to the list of viruses known to the software.
This was a valid process to a point as it was quite possible that the original virus could be mutated in the world outside the lab
This led to claims that a AV suite protected against many thousands of different infections but with a much lower number of those "In the Wild"
With the move to heuristics in the industry where the actual activity of the virus is looked for rather than a key piece of code this is done a lot less today.