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.
I believe the OP was one of few investors or trader who is lucky with a pump and dump signal group of course there are other investors with bad experience with the same group but are not here to share their own experience, we just had to be extraordinary careful not to fall for this cheap propaganda or probably the OP is trying to promote the group here of which majority of forum members here wouldn't rely on other trading decision especially from unreliable source, notwithstanding the best bet is to make proper research and decide on the most credible and reliable coin to invest on rather than to join all those pump and dump signal group.