The docs for staged rollout aren't entirely clear as they tend to leave that key piece of information out.
If you re-configure within Azure AD connect server, that will alter the settings tenant wide; once switched over to PTA via Azure AD connect, you can just disable the staged rollout settings in your tenant.
Usually, when you enter a UPN into the Azure AD sign-in screen, it evaluates the UPN suffix (@keyman .com) to determine how to route authentication for your password; this is also known as home-realm discovery (HRD). With staged rollout, instead your tenant evaluates the entire UPN, which is how it's able to send certain people to PTA and certain people still to AD FS.
Once you re-configure your tenant in Azure AD Connect for PTA, regardless of whether users are in staged rollout or if it's all the rest of the users in the tenant (aside from cloud-sourced users), PTA will be the authentication mechanism regardless. After that change, you can just go disable the staged rollout for PTA in Azure AD; the entire tenant will be changed to just evaluate UPN suffix (@keyman .com) for HRD and everyone will be using PTA.