default server/index.js duplicates proxied request logs

[ghost]

example app for reproducing issue

$ git clone https://github.com/efx/poc-bug --branch ember-cli-proxy-duplicate
$ cd poc-bug/test-app
$ yarn install
$ npm start
$ npm run start-proxy
$ curl -I http://localhost:4200/api/hello

Upon making a request to the API, I see ember serve's log twice for the proxy request.

I expect to see the log once.
Perhaps this is from the proxy middleware registering additional logging? https://github.com/ember-cli/ember-cli/blob/master/lib/tasks/server/middleware/proxy-server/index.js#L41
The default blueprint for ember generate server attaches logging by default as show in the dummy app: https://github.com/efx/poc-bug/blob/ember-cli-proxy-duplicate/test-app/server/index.js#L19

Output from ember version --verbose && npm --version && yarn --version:

ember-cli: 3.8.0-beta.1
http_parser: 2.8.0
node: 10.15.0
v8: 6.8.275.32-node.45
uv: 1.23.2
zlib: 1.2.11
ares: 1.15.0
modules: 64
nghttp2: 1.34.0
napi: 3
openssl: 1.1.1a
icu: 62.1
unicode: 11.0
cldr: 33.1
tz: 2018e
os: darwin x64
6.4.1
1.12.3