These two fields are exactly the same. The List/Record it pulls from is exactly the same. Is there some setting in NetSuite to change how a Multiple Select Field appears?

Yes it's this value in your personal preferences. What this is basically saying is if you have more than 2 entries in the drop-down, it will do the option with the double-chevrons. I realize these are not drop-downs per se, but that setting applies to these as well.

Oh my lord, I even looked there and must have walked right past it. Thank you kind sir!