Here is my opinion of what’s going on and why…
First you check your bags and they are screened by the Aruba airport security for items or materials that may pose a threat to the aircraft and passengers in flight.
Then you proceed through to the Aruba Immigration who process you out of the country. Your next step is the Aruba version of TSA. They may mirror TSA security procedures but are not “ordained” by US TSA or the FAA. They are also screening passengers who are not bound for the US.
You go through the food court and duty free area which is NOT considered a sterile area by US TSA.
You reclaim your bags in preparation to clear US CBP. You must have your bags with you to clear US CBP in case they want to inspect your stuff. They are looking for persons who may not be allowed into the US, may cause a threat in the US, or people who are in possession of contraband, undeclared or commercial merchandise.
Beyond the US CBP desk, US TSA has control. They mandate the security procedures. They routinely inspect and train the contract security company who perform the secondary screenings.
The process is the same for every international flight into the US. If you were to enter the US from a foreign port and have a connecting flight. You would have to reclaim your bag. Go through the whole Customs process and then drop your bag off and continue on to your connecting flight.
It is just compressed in Aruba since the borders are under the same roof and do not span an ocean.
There are some airports overseas that have a “bypass” system. They take your picture with your bag when initially checking in and if CBP wants to check you out they can tie the luggage to you based on the photo. There are rumors that it may happen in Aruba but it cost $$$$$.