This doesn't necessarily have to be the case. A couple of years ago when the large scale protests were going on in Hong Kong, authorities found people who were using Telegram, Signal, etc., by adding all phone numbers to their devices' address book/contacts list. Telegram quickly adapted and brought a new setting wherein others would only get to know you were on Telegram only if you had them in your contacts list. Telegram has been, and is, far superior in hiding your presence to others than Signal is.