This is because, in the section between Yamashina Station and Kyoto Station, trains of either the Biwako Line or the Kosei Line are operated concurrently, while the lines bound for the same direction are collectively called the Biwako Line (the direct destination) for convenience; the above descriptions are also in accordance with this rule.
これは、当駅～京都駅間では、琵琶湖線系統と湖西線系統が混在することから、便宜上直通先の名称を使うことで、同じ方向に向かう2つの系統を一まとめにしているためであるが、上記の記述もそれに従った。