"Trying to do consistent, smooth lines using a round brush? Good luck."
It just takes practice. As long as it is the proper size for the line you are making and it holds a decent point, though, it isn't so much of an issue. Rigger brushes are long-bristled, thin, and round and used for lines, after all.
A rigger brush is specialized for lines - a "medium round (the pointy but wide-ish one)" is not, and will most definitely frustrate a beginner who is trying to do good consistent line work.
The first rule for choosing a brush should be to choose the correct one for the job. Sure, an experienced artist will have better brush control, but this guide is for beginners.
It just takes practice. As long as it is the proper size for the line you are making and it holds a decent point, though, it isn't so much of an issue. Rigger brushes are long-bristled, thin, and round and used for lines, after all.