Is this just another scam, or is it actually possible that some people have genuinely profited from these groups?
I can't call this a scam even if they are not sincere with what they say, so long as they are frequently issuing betting signals to you, they've delivered their own end of the bargain.
Why would not you call it a scam? Most of those groups initially start by giving some free signals and then when people get hooked up to the channel and want to have further information is supposed to pay to the administrators of the group, and since we are talking about people who usually exaggerate their accuracy about their tips, most of the cases those Telegram groups are scams, seeking to exploit the needs of people and their greed to take their money and run away with it.
The only legitimate betting group which I could think of it would be one which does not ask for fees in order to give out tips to their members and does not promise anything unrealistic to their members.
If some administrator of those groups managed to have privileged information, they would not use that information to open a Telegram group, but rather to get rich with such information and tips. It would not make sense for them to share it, either for a fee or for free.