When building a release build of a parameterized job, the build parameters are not included in the form - only the release parameters are. The build parameters therefore get their default values, which may not be desirable.
It is possible to override the defaults by defining identically named release parameters. This has several drawbacks: config duplication, and confusing duplicate entries for the same name (with different values) in the "Parameters" list for the completed build.
I think build parameters should also be configurable when triggering a release build.