R260 removed the appcachse because "all major browsers now support Service Workers and AppCache is on the deprecation path"
According to MDN, Safari, neither desktop nor mobile, supports service workers.
I found conflicting information that Safari does support service workers in 11.3 and later.
But even if that is accurate iPhone 5 and below and iPad gen4 and below are left out. That is about 13% of iOS users.