This is certainly a scam. If they just wanted to be sure users are holding a good amount of TON on wallet, they could have always checked the balance of the connected wallet. If they wanted transaction activity, they could have just asked for 0.01 TON. A specific and large amount like 0.5 TON might turn into a scam as even though they distribute tokens, its value might not be over the value of 0.5 TON. Even if users makes profit for the talked project, such trend would surely make more and more scams.