I could be out in left field with my thoughts but I think your dealer is incorrect ... the In Command BCM merely supplies control voltage to the controller for your BR slide out.
The controller .. if the motors are synchronized correctly will receive signal from that controller to shut off power to both motors.
I’m assuming your slide out is the type referenced in this link I’ve attached
I’d look at Link page 9.. I’d also be curious to know what happens if you manually close that electric slide out by using manual over ride switch located on the BCM for that electric slideout...
If.. when using manual override switch on BCM to close that slide out it still is not closing tight at bottom then in my humble opinion the slide out motors are out of sync with what they think is the closed position or the controller for that slide out has an issues sensing the build up of motor current
https://lci-support-doc.s3.amazonaws...cd-0001602.pdf
https://store.lci1.com/blog/retiming...syncing-issues
In essence all the In command DC.. display commander is doing is taking a digitized signal and sending it to the BCM to latch the relay for that power line to send signal to controller to operate.. much the same as a conventional momentary in/out slide out switch is doing.