The source code is in .ts, and appears to use Node child processes [0], so probably yes. I'd be curious to see the kind of resource usage is involved building TSC.

My limited experience using Node worker threads (to compile small React apps with WebPack in parallel) showed lots of overhead and memory usage for just starting the build (Node and library instances, can't say in what proportion), although it is still worth the expense.

[0] https://github.com/microsoft/TypeScript/blob/master/scripts/...

A good question, though I will point out that either way benchmarking would still be useful.