Consider code like:
---
                com.sun.source.util.JavacTask task =
                        (com.sun.source.util.JavacTask) provider.getTask(compilerOut, null, null, options, null, inputFile);

                Processor processor =
                        (Processor) processorClass.getDeclaredConstructor().newInstance();

                task.setProcessors(List.of(processor));
                task.analyze();
---

This will produce warning like:
---
Note: Annotation processing is enabled because one or more processors were found
  on the class path. A future release of javac may disable annotation processing
  unless at least one processor is specified by name (-processor), or a search
  path is specified (--processor-path, --processor-module-path), or annotation
  processing is enabled explicitly (-proc:only, -proc:full).
  Use -Xlint:-options to suppress this message.
  Use -proc:none to disable annotation processing.
---

which is incorrect, as the processors where passed in using the API.