Correct. This is a current limitation in HMC, regardless of 1.x or 2.x. We will be adding the feature to select which hosts to run DataNode and TaskTracker in an upcoming release. Since it's an enhancement, we will not be backporting it.
In the meantime, you have the option of performing a manual install, where you have the most flexibility to choose which hosts run which services. This link is for performing Manual Install using the HDP 1.1 packages.