Lexicographic order is great when you need an unambiguous criterion that will work the same in every implementation; but you only need that for automated processing, i.e. for coding.
For user-facing presentation, having 5.9.xxx before 5.10.xxx is simpler; the corner case that baffles users is having 5.1 and 5.10 before 5.2.
Some (most) systems will sort 5.9 after 5.10 though, so if the user is baffled they'll need to learn it anyway. Adding a second way to do it kinda makes things worse
For user-facing presentation, having 5.9.xxx before 5.10.xxx is simpler; the corner case that baffles users is having 5.1 and 5.10 before 5.2.