The lineage folks didn't want to merge it in on grounds of security concerns.
(I'm not affiliated with the project, I just read the code reviews because I had the exact same question).
EDIT: for those interested: https://review.lineageos.org/#/c/64967/ and https://review.lineageos.org/#/c/65366/
So MicroG people created this fork with the patch builtin.
More info here: https://github.com/microg/android_packages_apps_GmsCore/wiki...
Also http://blogs.fsfe.org/larma/2016/microg-signature-spoofing-s... is an interesting read
No. LineageOS' developers hide behind the "security reasons" shield, but in reality they don't care enough about the freedom of their users to risk to upset Google by giving them an alternative to the Play Services."
LineageOS's have a policy of not circumventing integrity checks e.g.:
The people behind this ROM seem a bit immature if that's how they react to their policy especially since they're just taking the upstream code wholesale to stick their patch in.