It would be really great if this VERY important concept of Direct Object could be added to this lesson. - https://progress.lawlessfrench.com/questions/view/wrong-answer-nous-sommes-brosse . 

More importantly because, this lesson says this « Note that when être is used as the auxiliary in compound tenses such as Le Passé Composé, the past participle must always agree in gender and number with the subject of the verb.»  --- and this statement is not true for this lesson on reflexive verbs as per the link. It creates a confusion. Kindly rectify this incorrect statement and help us new learners with the necessary concept within this lesson, please!

Thank You.