Let me explain it with an example :
Orginal source : 10.0.0.0/24
Original destination : 10.100.1.1/32
translated source : 10.200.1.1/32
translated destination : 18.104.22.168/32
In my opinion, you are doing HIDE NAT for the source and STATIC NAT for the destination.
I have run a few a test with the API and although you can only define on method ( Hide or Static ) and seems R80.10 is somehow intelligent to know that this is for the source only. Translated Source is Hide in my policy, Translated Destination is Static in my policy.
This is what I've been looking for.