Your revolve feature is not a simple revolve, but a revolved thin feature. Thin features are ones where instead of extruding or revolving a selected 2D area, you extrude/revolve a line that has been converted into an area using a thickness offset. You could think of it like extruding/revolving a line into a surface and then adding thickness to that surface to create a solid. In your example the thickness value is large enough that most of the revolved area is filled in, except for that small area. Unfortunately once you create a thin feature you can't convert it back to a normal feature. You have to delete it and recreate it as a non-thin feature. It's not a big deal in your file since you only have one other feature after it, but it can be annoying in a more complicated part.
As for this being a good way to approach the part, that depends on a lot of things. It mostly just depends on what you want to end up with. It's also a good idea to think about how the part will be made. If it's going to be milled from a solid or cut with some kind of cutting machine (laser, plasma, waterjet) you probably would be better extruding from a 2D sketch. If it's to be 3D printed or molded then it doesn't matter as much. Design for manufacturing is a HUGE topic though so ultimately there are really no wrong answers, just better or worse answers.
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