enamel mug printing

[Chris16]

We have had botanical images printed on enamel mugs. The first batch of mugs had the same smooth shiny surface inside the mug as outside. The second batch had a rougher surface inside which tended to stain easily when used and felt of a lesser quality. Would this be because the first batch was coated for dyesub printing both inside and out and the second batch only coated for the outside printing?