Quote - in my understanding, there is no need to turn a figure into a prop.

Mostly, no; but it does depend on how the clothes were modelled. Some don't have their groups welded, and in that case, exporting with 'Weld body part seams' checked will fix it.

Often, vendors don't make details such as pockets, buttons etc. part of the mesh, in which case they will slide off when simulated. You can usually add them to the soft- or hard- decorated groups which will make them 'stick' to the underlying mesh.

However I have seen some clothes modelled in separate pieces (cough well-known Japanese vendor cough) and while these work fine as conforming clothes, they'll fall apart in the cloth room unless you join the bits back together in a modeller. When it gets to that stage I usually think I might as well make my own damn clothing. ;) Then again, some older clothing was modelled with closed end caps which intersect the figure and won't simulate at all. The only solution here is to remove the caps; PhilC has a tutorial on that at his site.

In other words, there is no single method. You have to take each item on its own merits.