When I make a call using the Dialpad app, a message pops up asking me to confirm placing a call to a different number.

I agree this is a little strange, but it is just part of how the app works. When you make a call from your smartphone, it needs to first dial into a Dialpad phone number to get into Dialpad's network; from there it places a call to your destination - that is how it is able to hide your personal phone number from being seen on the Caller ID of recipient.