However could it be a bug or could it be for competitive purposes that WhatsApp is blocking Telegram links on its Android app? According to reports on Reddit, it seems that when it comes to WhatsApp for Android, links to Telegram are being blocked as you can see in the screenshot.
As you can also see, the link to YouTube works just fine. It should be noted that this only seems to affect the Android version of WhatsApp as the iOS version is allowing the links just fine. Like we said it could probably be a bug that is causing the links to not show up.
This has happened in the past due to algorithms it uses in which it attempts to detect if certain links are spam and blocks them, like they have accidentally done so in the past with links to Imgur. In any case hopefully this is something that the developers are looking into and a fix will be issued soon.