/slow clap
If you had a road running east-west, I would wonder whether the trees on the north side of the road (i.e., with the road to the south) would experience more growth than the trees on the south side of the road (i.e., with the road to the north). Having a southern exposure means that you get more sunlight, and so the growth might be more vigorous for the trees on the north side of the road, causing an asymmetry.
All of this assumes we’re in the Northern Hemisphere, of course.
Maybe true in general, but the probably most-seen conifer in the U.S. (Eastern White Pine) is not very shade-tolerant, in fact is typically the first tree species to grow in open areas. And my impression is that it self-prunes pretty aggressively.
If you’re trying to make a lovely, tree-lined quiet avenue into something of a “tree tunnel” then you’re probably planting the same species on both sides. After all, you don’t want your symmetry ruined by different bark colors or one tree being gold in the fall while the other is purple. So you have two elms or maples or ash trees (unless you have ash borer, RIP ashes) on opposite sides with the same growth rate and spread and naturally they’ll meet in the center because both grow the same.
If you were to plant a slow growing oak on one side and a fast growing locust on the other then the locust will spread out faster then the oak. Eventually the oak’s branches may sort of push through but they wouldn’t be forming some symmetrical arboreal tunnel.
On most major roads, the tendency is to mix up the types of trees so a single disease or insect doesn’t take out every tree along the road. But these are usually larger, multi-lane affairs and will never become a sylvan paradise under the best conditions.