It's been a weird year for potatoes, earlies were poor because of drought, so some had raised scabby patches.
Mains have had to put up with too much rain and possibly flooding on some farms, leading to swollen lenticels, which can look very strange and off-putting if you haven't seen them before - so well done Tesco for explaining to customers.
Of course the other thing to bear in mind, is that if all the rough-looking ones are rejected this year, there won't be enough to get us through 'til next year....