About MRP Area (Storage Location) and MRP Area (Plants)

Why is the S/4 HANA MRP Area customization arsenic follows?

e.g.)
<Master Client (CL100)>
  Plant 1000 Storage determination 1001,1002,1003
  Plant 2000 Storage determination 2001,2002

MRP Area Customize (Set lone the pursuing retention locations)
  -MRP Area 'AAA' :Assign Storage determination 1001

After making the supra settings, erstwhile transferring to CL200,
<CL200>
MRP Area (The settings are arsenic follows erstwhile viewed successful SPRO)
  -MRP Area '1000' :Plant 1000
  -MRP Area '2000' :Plant 2000
  -MRP Area 'AAA' :Assign Storage determination 1001

*Question
Why are MRPArea1000 and 2000 automatically registered astatine the transportation destination? Is this modular SAP behavior?

Please fto maine know. Thank you.