Using "Drop" to replace sample - sample end issue

I’ve created a macro page with a Sample Display and a Drop element of the same size.
This lets me replace the sample by drag and drop onto macro page sample display.

The issue is the sample end doesn’t change to reflect the length of the new sample, if I drop the sample onto the macro page.

However when dropping a sample onto a zone in the program tree, the whole sample is displayed and the sample start/end reflect the new sample. Why is the behaviour different in this case?

Keeping my eye on this as this is something i need once i get my head around the whole macro thing, will try to work through this also