For a one piece panelboard (loadcenter) I think you could have different UL listings for different components.
I took a look at UL 67 on Panelboards. The standard defines panelboard the same as the NEC (almost, it appends "or placed in an enclosure" to the NEC definition), the term excludes the enclosure. The term "panelboard interior" is offered as a synonym. An "enclosed panelboard" is a panelboard plus its enclosure (actually its definition repeats part of the "panelboard" definition and then appends "installed in a suitable cabinet, cutout box, or enclosure suitable for a panelboard application.")
UL 67 7.1.1 says "A panelboard shall be constructed for use in a switchboard, cabinet or cutout box. An enclosed panelboard shall be provided with an enclosure complying with" UL 50. I didn't read all of UL 67, but the standard has a few other requirements for enclosed panelboards, such as when gutter space is required and how large it needs to be. I didn't see anything saying that the panelboard portion of an enclosed panelboard must be used in the provided enclosure.
So I believe that it's true that the panelboard's listing does not depend on the enclosure that it is usually provided with it. You can swap out the enclosure, although there are certainly clearances you are required to maintain.
Cheers, Wayne
P.S. As an aside, I was interested to note that UL 67 11.3.2 provides a way to compute the ampacity of panelboard rated for up to 400A aluminum busbars, 1600A for copper busbars, and forego the UL 67 Section 21 Temperature Test. It specifies an allowable current density of 1000A/in^2 for solid copper, 750A/in^2 for solid aluminum of specified minimum conductivity, and 200A/in^2 at bolted connections, with some exceptions.