We can use the Job executor, mainly for testing like:

        Job
                .components() //
                .component("emitter", "test://emitter") //
                .component("out", "QA://AssertionOutput?" + "configuration.%24maxBatchSize=4&" + configStr) //
                .connections() //
                .from("emitter") //
                .to("out") //
                .build() //
                .run();

As you can see in the example, it is possible to add the $maxBatchSize parameter: https://github.com/Talend/component-runtime/blob/06ac75da48799c8b758b5a720c34d64f9a69cd23/component-runtime-manager/src/main/java/org/talend/sdk/component/runtime/manager/chain/internal/JobImpl.java#L354

It is taken into account and by default it seems set to '1' since after group is called for each record.
If we set a maxBatchSize greater than the number of records given into "handler.setInputData(records);", the afterGroup is never called.
It is called if the maxBatchSize is lesser or equal to the number of record.
Should be great to call it when all records are processed.