Hello everyone !
I come back to this post with (I hope !) good news for you.
I think I've found a workaround thanks to the work template.
In the edit query of the work template that is used during the Goods in transit reception, I have set up the following criteria on the quantity :
Thanks to this criteria, I expect that the system will ignore this work template if the quantity that is about to be received exceeds the quantity of 10 pieces.
And because this work template is the only one defined for the "Good in transit" work order type, the system should block somewhere.
Let's make the following scenario:
We place a PO of 5 pieces for the Item A.
We create a voyage that contains this PO and we invoice this voyage.
During the reception process, we try to receive a quantity of 11 pieces.
First, the system give us the warning that we are about to complete an over reception of 1pc (it's because of the setup in the mobile device menu item I think).
Then, if we try to validate again and override the warning, we have the following message :

We can continue to validate as long as we want and the system will block because he can't find any work template to use to generates the GIT receiving work.
Note : I have done another example with a PO of 5 pieces and tried to receive 7 pieces and it worked. The system well generates an over reception of 2 pieces.
I hope this answer will help you and I wish you a wonderful holiday season !
Best regards