What distinguishes yāʾ in «فِي» from that in «كَيْفَ»?

Al-Fīl and Quraysh: Applied Iẓhār, Ikhfāʾ, Idghām, Madd and Waqf

• Madd yāʾ first, līn yāʾ second
• Both are always connected madd
• The first has nūn sākinah
• Both have a doubled yāʾ