I know this is a bit late, but I read on a web page that they still do the vehicle inspections, but at the border. Though this is not an official CBP page, it would make sense for them to do this.
https://www.bajabound.com/before/permits/sentri.php"Vehicle Inspection Guidelines
The SENTRI program no longer requires a vehicle inspection appointment. Now you will be passed to secondary inspection one of the first few times you cross back into the Unites States with the vehicle."