Not unusual for FT to screw up descriptions, I'm sure that is the case here. The chimney appears to be somewhere between 5-10 mm shorter, not a huge difference, but enough to change the look, and possibly improve flavor slightly.
Any tank which has a "nano" kit available I've purchased, as a rule it improves flavor. Capacity will obviously be reduced, which does not bother me, but to some that will be a negative.
Going by the picture that glass looks to be very near 20ish mm in height.
I'll be ordering a couple to try them out along with the Taifun III

. Merlin is still my favorite single coil tank.