I found a Sans last week that struck me because of its unusual new growths. The original growth appears to be robusta, or black robusta. The two new growth have leaves that are almost solid green but are thicker and more rigid. They have a longitudinal line down the back of the leaf like a spine. The front of the leaves have two fairly deep grooves running longitudinally. All leaves on each of the two new rosettes display these characteristics. The original plant has none of this.

This is the original plant:

These are the new growths, back:

And front:

I am asking for opinions. Is this a fluke or is something else growing here? Thanks