No.
And it isn't a silly idea, it's because of backwards compatibility.
Like many other applications (Remote Access Services, Services for Netware, Lotus Notes), in Windows NT 4, Terminal Services stored its user configuration information in an application specific opaque blob in the NT Domain user object.
To ensure backwards compatibility, in Active Directory these services still store the application specific information in the userParameters attribute.
Some applications, for example RAS, while being administered through a COM API, also duplicate this information in RAS specific attributes, but alas Terminal Services doesn't.
The only way to modify this information is via a Terminal Services COM API. Perhaps one day when there is guaranteed to be no vestiges of NT4, then this configuration information may be stored in appkication specific attributes, rather than in a binary blob.