He probably was screwed either way in terms of his future at the company, but he should refused producing the document with these corrections. There was a tiny chance that maybe his resistance would make employer reconsider that.
Anyway if the company requires him to produce it, it means his purpose was to be thrown under the bus if the fraud would come up. In fact it sounds like the zoom call scheduled might be exactly that (director claiming he had no idea).
It is be best to have evidence stored in a safe place (or if control of the employer) if something bigger comes out of it.
At this point the client has a document with clear lies signed by that engineer, and the employer won't cover for him, so it doesn't look great.
