Does Usability Tests and Product Experience Maps go Under Discovery or Define Stage?

I'm creating education materials for my company on UX to help better educate the team and secure more funding for UX at the company. But as I was reading how we define stages of UX I came across what seems to be a paradox / conflicting information.

The discovery stage to put it very briefly as I've understood it is to explore the problems whether it be on your own product or problems prospective users may be facing, building empathy. Then this moves to the Define Stage where the team forms alignment on evidence based results from discovery.

I always assumed Usability Testing was part of the Discovery Stage and you can build personas and experience maps based off of these in the define stage. Because if the Define stage is to form alignment, an experience map allows you to take pain points and convert them into goals which hands off to the development stage.

However in my research I see that Usability testing is not often put in the "Discovery Stage" Example here and here .

In the above examples only user interviews are included. Usability tests can include pre and exit interviews which aid in the discovery stage. Usability tests also help discover what problems users are facing. So why are these left out?

I see Usability Tests are Discovery and Product Experience Mapping as defining.

But I don't want to commit to this on paper without reaching out to my fellow UXers and hear their thoughts and get some guidance. I never tried to break down the process so defined before and I am running into material that makes me feel my process of DISCOVERY Interview -> Usability Test -> DEFINE Experience Map -> Personas -> DEVELOP STAGE is wrong.

Thanks for all those that contribute in a positive way to this discussion.