I believe this is a limitation of the new presentation implementation first introduced in vRealize Orchestrator 7.6. Per the vRealize Orchestrator 7.6 Release Notes:
The input parameter constraints of workflows created or edited in the vRealize Orchestrator Client do not automatically transfer to the XaaS blueprint request form in vRealize Automation. To use these workflows in XaaS operations, you must manually define the input parameters constraints in the XaaS blueprint request form. This limitation does not impact workflows created and edited exclusively in the Orchestrator Legacy Client.
There were apparently several changes made with the new HTML IDE client for vRO that prevent backward compatibility. The release notes in 7.6 also explicitly state:
Workflows created and edited in the new HTML5-based vRealize Orchestrator Client are not compatible with the Java-based Orchestrator Legacy Client.
I have yet to test this in vRealize Automation 8, but my guess would be that the same issues exist which prevent presentation layer logic from working in the XaaS form.
Possibly - I need to research it more as well.
What I did was I imported a VRO workflow from v7.5 to in 8.0.1. and then created XaaS blueprint from that.
In v7.5, the XaaS blueprint presentation would copy / use VRO workflow presentation logic.
In v8.0, the XaaS blueprint presentation logic is empty / missing...
Hence I'm wondering if this is coming or not ... ideally someone with roadmap would answer this.