Uninstall the Telegram watchOS app: iOS Watch App > Telegram > Do not show .
When receiving several notifications on the Watch, it's not possible to see all of them when tapping the group, it just shows one.
Only the first received notification is shown
The group of notifications is expanded and you can preview all of them
Telegram 7.2.1 (18320). Watch Series 4 (7.1), iPhone X (14.2)