I think it's a "mental autocorrect"; there's far more names ending in -stein than -stain. You may amuse yourself by clicking on these links sequentially: https

I think it's a "mental autocorrect"; there's far more names ending in -stein than -stain. You may amuse yourself by clicking on these links sequentially: https://en.wikipedia.org/wiki/Berenstein https://en.wikipedia.org/wiki/Berenstein https://en.wikipedia.org/wiki/Bernstein https://en.wikipedia.org/wiki/Bernstein https://en.wikipedia.org/wiki/Berenstain https://en.wikipedia.org/wiki/Berenstain