Earlier quoted context omitted.
"Synthetic biology" in technical usage refers to custom sequences which are written on a computer then chemically assembled ex vivo . This is a widely used technique. It is distinct from the technique of extracting and amplifying a sequence from one organism and inserting it into another, although the results produced can be similar. Source: I work in a molecular biology lab.
So let's say there's a gene that might be useful to me. I have a listing of base pairs, but it would be very expensive to extract DNA/RNA from actual specimens. I chemically assemble an exact recreation and inject it. Is this synthetic biology?
Yep! Although the result might be the same, the technique used is synthetic biology. Usually the synthetic route is more expensive but a lot simpler.