i can’t figure out why they didn’t top it with razor concertina wire and sharks with lasers ...
“why they didn’t top it with razor concertina wire”
The Military has been emplacing the concertina, out of the DoD budget, so DHS dollars can buy more miles of wall.
They will generally wait until the whole construction project is finished (unless operationally urgent) - until the Contracting Officer accepts delivery of the finished project, after final inspection.
That way, there is no re-working, if the contractor has to fix something, and they don’t get in each other’s way.
The Military deployment to the border, which includes Combat Engineer support to emplace concertina and harden Ports of Entry, has been extended through FY20 (30 September 2020). They will emplace hundreds more miles of Concertina before the election.
I would bet a months pay, that a high priority place like San Diego will get complete coverage with concertina. It is very effective in defeating ladder and rope attacks, which is the only reasonably easy option remaining for crossers there.