[ronaldx]

I agree with what you say.

To correctly compare the variances, the scale should be adjusted according to the square root of the ratio of sample sizes.

The author has not done this correctly, but I claim that zeroing the axis would be further from the correct graph.

[craigmbooth]

Ah, you are correct, thank you. Apparently I wasn't thinking clearly when I normalized the axes to have the same absolute ranges.

[sesqu]

I generally feel that zeroing the axis is never wrong, but yes, in this instance a (properly) cut axis would be better than correct. However, it should be apparent at a glance, and the presence of the other two graphs complicates things as well, so I have some reservations.