So quite literally it's just a hole cut out in the pipe allowing air to leave the tip earlier, essentially allowing for a greater cross-sectional area for air to escape without the use of bigger pipes? I think that in this case the Bimodals would be contributing more to the noise of the engine, right?
In the article I linked it was said the baillie tip directs sound onto the boot floor but as the cutout looks, it can only direct sound backwards. The outer exhaust tube (the shiny decorative bit) is sealed to the inner exhaust tube at the front and open at the rear while the hole you see is in the inner exhaust tube... the tone that such makes must depend on airspeed, hole size and chamber volume between the outer exhaust tip and inner exhaust tube...
And I doubt the floor resonates in any way to add to the aural pleasure while all the insulation they put in modern cars will work at cutting any sound and vibration transmission into the cabin. Most of the sound you hear inside is from the motor sound enhancer (that plumbs intake sounds through a diaphragm and into the cabin via a pipe) unless you open a window.
If you’ve ever played a wind instrument, think of the baillie tip as a flute you poke into a large pipe. When you start to play some sound will be directed back at you
Whether a baillie tip would sound as good in a Ute is anyone’s guess but I’d have assumed the magnum has such an exhaust and I’d expect they’d sound better than the run of the mill utes. Maybe one of the magnum owners can chime in