It is considered that such changes in the announcements were made because trains of only one type (local trains for Uji) are operated on the Uji Line, but another reason is to prevent passengers going to get on a down-train on the Keihan Main Line on Platform 2 from mistakenly boarding the train on Platform 3 or 4 when a train is going to depart from Platform 3.
これは、宇治線内では1種類の列車（普通宇治ゆき）しか運転されていないことと、3番線発車の場合は2番線に発着する京阪本線下り列車との誤乗を防ぐためと思われる。