Hacktoberfest is an event intended to help people contribute to Open Source. Based on this, the statement is false. If your only objective is to get a t-shirt,

Hacktoberfest is an event intended to help people contribute to Open Source. Based on this, the statement is false. If your only objective is to get a t-shirt, sure then it limits you. But if your objective is contributing to OSS, nothing is stopping you of making meaningful contributions! The only change is getting the t-shirt, but sylveon's comment sounds a very generic statement so wanted to clarify that open source actively welcomes contributions.