But Safari for iOS is still pretty standards compliant, performant and modern, and far better than Android as a whole when you consider the huge chunk of Android users on an old version of Android that will never see an update (the same users who will just use the default baked in browser). Saying iOS isn't supported would generally be artificial constraints on the part of the site builder on principle, not an actual practical issue with serving them a web page.

You'd easily be shown to be the asshole when a jailbreaker or someone with a proxy spoofed their user agent and loaded your page just fine. Not supporting a browser without a valid technical reason that the layperson can ever sort of understand will totally undermine your position.