In Verbs Present 1,the notes state that all verbs fit into 3 groups: -er ending -ir ending -irregular verbs Where do re ending verbs fit into?
In Present 2, another group is added and still no -re verbs and Present 3 has no tips and notes.
Interestingly, two -re verbs are discussed in Verbs: Present 1, connaître (irregular) and attendre.
There are five irregular -re verb patterns and the irregular verbs are supposed to be in the 3rd group, so perhaps they decided to consider the group of "regular" -re verbs as an irregular form of the 3rd group of verbs as the only difference is the third person singular does not have -t added to it. Imagine how hard it is for beginners to learn a regular -re verb pattern, only to find out there are 5 more groups of -re verbs which are irregular and different from each other. Interestingly, the 4th group of irregular -re verbs does take the -t in the third person singular and are exactly like that 3rd verb group on Duolingo. Did they decide that this group was actually larger than the -re group that many language courses teach as "regular"? Perhaps with the addition of other non -re groups with similar endings, this set of endings may have ended up being a larger group.