I got an answer from Sitecore support (see below). It indeed has todo with the order submission pipeline and that an outcome hasn't been registrered. After enabling the TriggerOrderOutcome processor the Orders tab in the Experience Profile shows orders as result.
As for the reported issue, I am able to reproduce it on my side. The
issue is related to the fact that the mentioned tabs get the data from
Commerce->Overview tab reports all the orders which were registered as
interaction. whereas Commerce->Orders tab reports all the order which
were registered as a
The Sitecore.Commerce.CustomModels.Outcomes.SubmittedOrderOutcome is
registered on a submitVisitorOrder pipeline.
But as far as I can see the processor is disabled by default.
In order to make it register such a type of data, please open the
"App_Config\Include\Sitecore.Commerce.Orders.config" file and
uncomment the "Sitecore.Commerce.Pipelines.Orders.TriggerOrderOutcome"
The behavior you reported was registered as a bug in our bug tracking
system. Thank you for reporting the problem.
To track the future status of this bug report, please use the
reference number 329511. More information about public reference
numbers can be found here: https://kb.sitecore.net/articles/853187