There really is no good way to animate a profile spline growing along a path spline. The only way I can think of would be using a path deform modifier, but that stretches the geometry along the spline in order to sort if "fake" the growth. That becomes problematic if you want to maintain the consistency of your subdivisions as it grows.
The only real other way to do it is by animating a loft, but that is aggravating because you have to use the points on the loft graft to animate the profile spline growth. Not very intuitive.
Check out Cinema4D's Sweep object for inspiration 😉
Also. Could we maybe up 3DSMax's motion graphics game a little bit? You guys were trying to go in that direction about a decade ago: https://youtu.be/9VVBD6wVzvU
What happened to that?
Bring MASH over to Max, or something like C4D's Mograph tools (cloner, fracture, MoSpline, MoText). That would be a very welcome addition, and those types of tools could help streamline a lot of processes in Max, even beyond just motion graphics.
