Just recently what i used to confirm if a Office 365 Group was Teams enabled or not was this one-liner:

Get-MailboxFolderStatistics -Identity TestGroup -IncludeOldestAndNewestItems -FolderScope ConversationHistory | Select-Object FolderType

If there was a conversation history foldertype of TeamChat, the group was Teams enabled.

I  got a question from one of my blog readers if there was another way to check this?
He asked this because my groups check was not working anymore. It had worked a couple of weeks ago. What had changed?

I tested by creating a new Office 365 group. What i found was that the group contained the conversation history foldertype TeamChat without beeing Teams enabled. I even checked groups in my Office 365 Tennant that was over a year since they had been created. These also cotained the TeamChat folder type.

It now looks like Microsoft for some reason are pre-preparing Groups for Teams.