This.I think it's quite obvious, esp. when you compare more than just phaser/flanger:
Those blocks with not-so-many types open the small list (like the phaser block) and blocks with lots and lots of types open a scrollable, searchable, multi-column window (like the amp or flanger blocks).
Today I learned...Shift+Click any dropdown will open a picker window. Adding the Control (Windows) or Command (Mac) key to the sequence will open the picker window with the pin down.