Good point, Daisy!
Look at the 2nd detailed photo of your first plant. Top center left between the spines you will see a bit of wooly white 'hair' in between the tubercles - which carry the spines.
In your second plant it is not as easy to see but it looks like it may have it too.
Some Mammmillaria have this wool in profusion and year round, whereas in many others, these tufts of wooly white hair tend to be way more pronounced as the plant builds up to flowering, flowers and then shortly after, in the non flowering period they diminish in prominence or sometimes almost completely disappear until the next flowering cycle.
The M. haageana I posted a picture of shows a very small increase in the tufts when it flowers, but it is pretty sparse. However this is another one - just a different ssp. (likely ssp. elegans) that clearly shows the tufts very prominently in the band with the flowers and much diminished outside of those bands.
