Nice looking plant. Like I have said (from someone else), 'You can't judge a plant by one leaf'. Now if from a pup!! Then you might have some promise. I know S. tri. Bantal's Sensation does grow large but mine seldom gets over 18 inches. Yours looks so much taller than mine.

Russ from Florida commented on mine last year about another variety of Bantal that was greener but I only get a strange leaf or two like you.

I have a couple of weird leaves on mine. One is shorter, wider and has that same edge.

It seems the variegation isn't particularly stable since it is reverting in that section. Looks very nice though, love it!

Watch that pup to see if it's just one leaf or a growing pup. If so, I would remove it and grow it out on it's own to see what develops.

I have to admit those look so much nicer than mine. Shamed to show mine now.