"Found it!" – What was the point of posting this question then? It will be closed as a duplicate of the one you have found. Unless… Unless your primary question is "how can I configure
sudo to not do that?" and the answers to the other question do not solve this. Doesn't Defaults !fqdn solve this? I totally don't know. If this is the case then please [edit] and rebuild, concentrate on the actual question (e.g. the title should be different) and clearly state that the alleged duplicate does not solve your problem.