> No, GP means, literally, who put the cage policy in place. It was not the Trump administration.

The policy of deliberately maximizing use of the cages by maximizing family separation and using the induced psychic harm as a deterrent is a policy adopted by the Trump Administration.

The policy of requiring segregated detention of children, when actually detained, which caused the cages to be necessary was a judicially-imposed policy.

The policy of minimizing detention of children so as to minimize the use of the cages, including not detaining adults accompanying children without reason beyond illegal crossing, was a direct response to that judicially-imposed policy by the Obama Administration that was abandoned by the Trump Administration.

So, if one is using “built the cages” with the peculiar meaning you suggest of “adopted the policy for their use that is the subject of the objections”, Trump “built the cages”.

Here is a photo of children put in cages during the Obama admin[0] by Donald Trump.

[0]https://media.npr.org/assets/img/2018/06/18/ap_1816885517410...