In the lesson it explicitly states "Note that in French, if you're using après + [verbe], we consider that this action always takes place in the past of when you're speaking. "
However the following was a question for the tests on the lesson.
"After going food shopping, I'll help you with your homework." This is neither 'said in the past' NOR actually already happed(ie 'in the past'). While inelegant, it means "After i go shopping I will help you ..." The stipulated correct answer was "Après avoir fait les courses, je t'aiderai avec tes devoirs.'
Seems to fit the following translation "Apres je aurai fait les courses, je t'aiderai avec tes devoirs. Since both aactions are scheduled for the future with the homework help being predicated on the shopping being done.