different file size and the number of point cloud between two chunks

[bigoo]

Hi,
I have a question about the number of dense points and file size.
When I surveyed the study area, area a was shot with full frame dslr and area b was shot with insprire x5.
Area a has a steep slope, occluded surfaces occurred during vertical shooting, so I photographed with dslr on the land, and area b is a flat and large area, so inspire x5 was used.
Area a and b are in the same space.

When building a dense cloud, I used two methods.
Scenario A: Modeling was performed by simultaneously inputting the shooting results for areas a and b.
Scenario B: After building a dense point cloud individually for the shooting results for area a and b, I merged the two chunks(area a and b).
By the way, the number of points in scenario A is 808,987,475 and the file size is 11.37 GB. The number of points in scenario B is 462,749,625 and file size is 6.79 GB.
I expected the results for scenarios A and B to be similar. However, the modeling results were almost twice as different as mentioned earlier.
What is the reason for this?
If it’s possible, I’d like to give my two reports.