Pump group? Man! You have to be careful, I have friends who have lost a lot from such groups. Although, I don't know how legit this one is, you have to be careful. Is best you get insights yourself from any coin you wish to buy. Even Binance, Bitget and some other exchanges do give insights into coins that do well. You can start from there if you wish
The advice you say is completely logical and not wrong because basically everyone has to rely on their own knowledge regarding anything, including trading. Pump groups can also play bad intentions and roles when they see that one of the participants has more money in it, so it would be wise for anyone not to rely on other people's thoughts in trading except based on their own thoughts on any coin on any exchange. And the loss that befell your friend can also be a good enough example for everyone to no longer trust any pump group.
sometime trading signal also giving outright half assed information too where it could mislead people, thats why its always better to be able to analyse by ourselves because if there's misleading information by these signal group then we can know beforehand and not fall to be a victim. but i guess many people won't bother with making their own analysis since just relying on trading group if it could give them profit despite just some small amount they are fine with it considering the fact that it doesn't require them to be doing some complex thing that might make them exhausted but the cost is indeed the capital thats at stake here, the signal giver might be giving misleading information for the sake of creating exit liquidity for them.
sometime people won't believe that these pump group might be the reason you went out of business doing your trading before experiencing first hand massive loss caused by following their signals.