It makes sense that new rules should apply to newly made/sold phones. Why not grandfather existing phones? Isn't any communication better than none in an emerge

It makes sense that new rules should apply to newly made/sold phones. Why not grandfather existing phones? Isn't any communication better than none in an emergency? A working phone, even if it doesn't support placing official emergency calls, would still be able to place a phone call for help. Even sending an email or WhatsApp message is better than nothing. This makes me wonder, is calling the emergency services number (911 / 119 / etc) now restricted to only such mobile phones officially supporting the protocol? This means you can't dial the emergency number from a pay phone or landline? I'm really confused about the underlying logic here.