Teams : files and posts (posts <---> files / order preference)
I don't think natural that the first tab for each channel, is the tab "posts". In certain cases, the user wants to create a team to talk about something, in other cases he wants to use it as a place to archive datas. Microsoft should let us the freedom to choose which tab will appear at first sight. Actually, only the third one (wiki) can be changed.
By that way, I understand that Microsoft wanted to encourage ourselves to change our behaviour in the organization of our "folders" (in explorer) who became "channels" in teams. And obviously also to show us the way to follow in terms of communication, cooperation en collaboration.
But it also depends on how the user wants to manage his channel, how he wants to use it : as a files server (to archive), or as a place to chat (meeting room).