Does the account change when I modify the requasirrion from the requsition pool?

I have created a purchase requsition for an expense item A where the account is 2.66666.999.000

 and it is approved

go to autocreate pool

query the requisition

got o tools

modify

chnage the item from item a to item B

where item B has an expense account  2.677777.000.000

the account did not change is this a bug or standard functionality