https://va.ecitizen.gov.sg/cfp/customerPages/moe/explorefaq.aspx?utm_source=moe-corp-site&utm_medium=referral　

问：How is the 30 months stay requirement period applicable to my child’s P1 registration?　

答： A child who gains priority admission into a school through his/her distance category is required to reside at the address used for registration for at least 30 months from the commencement of the annual P1 Registration Exercise on 3 July 2019. If this condition is not met, MOE reserves the right to transfer the child to another school with vacancies, as the priority admission to the first school was based on the declared address used for registration.

只有你的距离帮助你获得了录取学校的优先权时，你才需要在这个距离内呆30个月。那位层主问的情况是，根本连抽签都没有，所有人都可以录取，不论远近，那么她没有利用这个距离获取优先权，所以就不必适用这30个月。