Hi @buzzcode
Developer accounts created under *.okta.com are designed to be used by developers in creating OpenID Connect apps. This modification makes it also easier to convert a developer tenant to a potential production tenant for companies.
Okta preview orgs are used by Independent Software Vendors in order to integrate their applications in Okta Integration Network and make them available to a wide range of customers. This is the reason for why SAML is enabled by default under application integration wizard for this type of orgs.
If you would like to use SAML in your developer org, then I recommend checking out the Enterprise developer edition. You can find out more details about it here.