"Authenticating Your Domains" documentation confusing

Hi

I read:

Using SPF AuthenticationThe domain in the envelope sender (also known as the MAIL FROM, bounce, or Return-Path address) must be registered in the Domains section of Certificates, Identifiers & Profiles. This domain must pass SPF validation, and the registered domain and envelope sender domain must match exactly to pass the private relay service SPF check.


But the examples at the end of the page are not SPF examples, well the syntax is, but it's more like Sender Id you deploy that way.
(the examples are not validating the returnpath domain)

SPF TXT Record for example.com to support using SendGrid
example.com. IN TXT "v=spf1 include:sendgrid.net ~all" Learn about configuring your SendGrid account.


SPF TXT Record for example.com to support using Amazon SES
example.com. IN TXT "v=spf1 include:amazonses.com ~all" Learn about configuring your Amazon SES account.


SPF TXT Record for example.com to support using Mailchimp
example.com. IN TXT "v=spf1 include:servers.mcsv.net ~all" Learn about configuring your Mailchimp account.


So what's the real requirement, SPF or Sender Id ?