General question on blood line designations

I have noticed that when I read the blood line designation that the baptism record and the marriage record don't always coincide. In one the family member will be designated mestizo and in the other Espn. Does anyone understand why this would happen? My guess is maybe the priest didn't ask and just made a judgment from looking at the individuals.

Another question I have just come across is a baptism record where the individual was listed as hija legitima but then only the mothers name was listed. Any insight would be appreciated, I'm thinking maybe the father died before the birth but this is just a guess because I can't figure out how the baby would be legitimate if the mother didn't have a spouse.