I have 6 LED undercabinet lights that I plan to link together and power using a switched outlet. The lights use SPT-2 linking cables with proprietary connectors that aren't long enough to link the lights so that the cord is hidden. I would like to use a spool of SPT-2 wire to connect these lights, but according to the NEC, SPT-2 wire can't be spliced (I would need to splice to connect the lights with the proprietary connectors; essentially I am just extending the linking cables). Can SPT-2 wire connections be made in a UL-compliant junction box mounted to the underside of the cabinets?
Here's an example of the junction box: https://www.homedepot.com/p/GE-Direct-Wire-Linkable-Fixture-Junction-Converter-Box-White-39971/304228493
This box is intended for the connection of AC power to the proprietary connectors, but I was wondering if I could use several of these boxes to make connections between SPT-2 wire and the linking cables. I am not sure if this would constitute a violation of code. Linking cables are available on Amazon, but they aren't long enough.
Edit: here's the lights I'm using - https://byjasco.com/honeywell-18in-linkable-plug-led-under-cabinet-fixture