I understand what you're saying, but I don't understand how dialing 123*45*67890 is any faster than dialing 123-456-7890 (or finding a PTT number in a contact list is any faster than finding a PSTN number).

And yeah, you can move some delay time from the beginning of the call, waiting for someone to answer the ring, to the middle of the call, waiting for someone to respond. Of course, you also have no feedback that the person received the message at all and you might be waiting for a response that will never happen.