All the other apps does it, Telegram, messenger, workplace chat, slack. Android allows name that includes special characters. If you share a file through Android's Intent API, Teams should filter out invalid characters.
Most of the utilities App I used export file with timestamp in name, and they include 20:10:10. It doesn't make sense for app developer to fix this since it's Team app's issue. Telegram simply remove these characters so you can share any file you want.