At about the 2:41 mark, Jonathan switches to object mode and adds sd surface modifier, and the topology of the object is still visible. However, when I was trying this, all of the detail seems to disappear when I switch to object mode. Not a huge deal, as I can switch back to edit mode to see detail, but I'm wondering if I'm missing something in my settings that's making my display look different than in the example in the video. Screenshot below. Thanks in advance! 
Hi Vanessa,
Jonathan has the wireframe overlays turned on. You can find the setting in the viewport overlays on the top right corner of the viewport and check the box next to wireframe.
He turns them on just to show the views the geometry, in reality you don't usually work like that. When you want to inspect your geometry, you always do that in edit mode. Wireframe overlay being off by default is because you don't actually want that getting in the way. You turn it on for aesthetic purposes mostly, showing off your good topology and stuff like that.
Thank you both! Turning the overlay on worked. But, thank you for also explaining that this is not the typical workflow.