In Odoo V13, I created a Product A with Costing Method using First In First Out (FIFO) 
And with 3 location 
Stock/Location A
Stock/Location B
Stock/Location C

When doing the inventory adjustment with Product A, add 100 unit with cost 0 in Stock/Location A, I will have 100 unit with $0 valuation. 

Then, few days or after I do another adjustment for Product A, add 100 unit with cost $1 each to Stock/Location B, it will result 
Stock/Location A, 100 unit, $0 value 
Stock/Location B, 100 unit, $50 value. 

then, I after I do another adjustment for Product A, add 100 unit with cost $1 each to Stock/Location C, it will result 
Stock/Location A, 100 unit, $0 value 
Stock/Location B, 100 unit, $50 value.
Stock/Location C, 100 unit, $66.67 value 

From this case I can conclude that the system is using average method to calculate the stock inventory value. 

and check the posting after created Sales Order and delivered out Product A with 100unit from Stock/Location A, the stock interim (deliver) is using $100 to do the posting. 

Is there any method we can configure the value base on FIFO instead of Average, is this bug?