How should ProcessInstanceHistoryLogQuery be returning variable updates? I

I am using createProcessInstanceHistoryLogQuery to get the history for a process:
historyService.createProcessInstanceHistoryLogQuery(process.id).includeActivities().includeComments().includeFormProperties().includeTasks().includeVariables().includeVariableUpdates().singleResult();

I am finding this returns ALL variable updates,not just those relevant to the process id I passed in. If logging is turned on, the flowable sql for updates and form properties is:

Preparing: select RES.* from ACT_HI_DETAIL RES WHERE RES.TYPE_ = ? order by RES.ID_ asc 
Parameters: VariableUpdate(String)

Preparing: select RES.* from ACT_HI_DETAIL RES WHERE RES.TYPE_ = ? order by RES.ID_ asc 
Parameters: FormProperty(String)

The other queries include the RES.PROC_INST_ID_ = ? to limit to the process id specified.

Is this a bug, or am I calling the includeVariableUpdates and includeFormProperties incorrectly? Or misunderstanding what they should be returning?