I have to disagree on that point. The video showcases the Procreate App, which doesn’t have a magnetic lasso feature.
I use both Procreate (the app showcased in that video) and Krita, nearly daily and use the selection features in both for creating shadows and filling in color flats for comics. That said…
Having reviewed the video (specifically within the timeframe you noted), it’s my opinion the feature you’re seeing in Procreate works like Krita’s Freehand Selection Tool. Only, with Procreate you’re allowed to lift your pen off the screen (which is because it’s a touchscreen tablet-based app, so the pen isn’t tracked in the same way a display tablet is for a PC). When you place the pen down again, a straight selection line is automatically connected between the point you lifted your pen up, and the point you placed the pen down again. The closest thing to that in Krita was previously noted by the others, where you use the Freehand Selection Tool to start a freehand selection and, when you want to lift your pen, you’d hold Ctrl down. You’d then place your pen at the next position and release ctrl. This action essentially results in the very same selection style but requires the modifier key to work.
Each applications method for this has drawbacks for me. While it’s nice not needing to hold a key down to lift your pen in Procreate, it often leaves me searching for the point I started the selection, because you must click the node to close the loop. The reverse, as Krita handles it, can also be troublesome, because if you just carelessly lift your pen, the loop will atomically close with a straight line and could lop off other areas of your selection by mistake.