R42500 R47500 and customer setup - partial order shipment/ partial line order shipment - Question

dear community,

customer setup / Billing information screen :

several options to manage partial shipments:

- flag 'partial shipments allowed' APTS

- flag 'partial order shipments allowed' SI01

APTS unchecked means that the system does not allow partial shipment.

I am unclear about the function while using R42500 for mass ship confirm

I ran a test with 'no partial shipments allowed'

I created a SO with 2 lines

- line 1 - ITem A quantity 1, no inventory available

- line 2 - item B quantity 1, inv available Yes

using R42500 to ship confirm

-> result is :

line 2 is shipped, status update

line 1 is not shipped, no status update

in short, what is the relation between APTS and R42500