Confused about Blogger custom domain and redirect

I had a blog using a blogger sub-domain, which earlier today I converted to my custom domain via blogger settings. I subsequently reconfigured my DNS settings for my custom domain to point back to Google. All is well and my blogger site is now running with my new custom domain.

I've followed most of the migration guide, imported my posts, and fixed up the permalinks so they match the blogger ones.

My question is, why can't I leave the Blogger custom domain setting the same, and just flip the DNS records for my custom domain to point to my Wordpress IP?

Wouldn't that negate the need for modifying my old blogger template with redirect "hacks"? Or will Blogger see my DNS isn't pointing to Google anymore and will stop the redirection?

@vDerekS Yes, you can change the DNS for your custom domain and point it to WordPress hosting account. Since you have changed the blogspot URL to custom domain, so what about the old blogspot links which have with it. You can see number of results in Google search for your old URL site:http://derek858.blogspot.com/, these links will not redirect towards WordPress, once you point hosting IP address to custom domain. That's why you need to add redirect code in blogger template. Thanks.