Actually planning poker is a great way to reduce the risks of task familiarity. Yes, it’s sometimes a risk, not always a benefit. First, it might lead to blind spots. ‘Been there, done that’, not noticing the subtle nuances that make this project diffferent. Second, the person estimating is not always the person executing. The discussion in planning poker between the experienced and the inexperienced helps the inexperienced learn from that task familiarity while meanwhile fostering discussion between the team. The discussion leads to an estimate that is based both on the input of someone familiar with the problem, and the inputs of others who are new but may have to attempt this feature.

If you estimate based on familiarity alone, you might fall into the trap of having the estimate done by only the lead developers.