In Arc, with taking no additional steps, as long as I have an attachment-enabled feature class, by clicking on the HTML Popup Tool, I get this. Emphasis on no additional steps.
All I did was click one button, there's my picture. No Additional Steps......
I can click on the image in the pop up...and the image itself pops out, and is larger.
In Pro, let's start with the so-called "Identify Tool":
Online documentation tells me that a series of many steps is the way to achieve the same result:
Go to Map or Edit Ribbon -> Select -> Pick a select tool -> Attributes -> Double Click on the attachment. (That's 5 steps BTW....)
Do nothing, one button, one step in Arc. The "button" is on the toolbar no matter what I'm doing in Arc. There all the time. Extra steps in Pro.