Hola William

We're using the preterite in the English translation because with the time adverb "hoy", today, the preterite is commonly used in English (rather than the present perfect), however it is the other way around in Peninsular Spanish. I can see your focus is Latin American Spanish, where the use of the preterite is actually more common (like in English). 

This example is from a lesson about nouns and their gender, which is content that is valid for both Peninsular and Latin American Spanish, but the examples in these standard lessons are a variety of these two variants. This is why you may find examples that reflect a bit more what is said in Peninsular Spanish and sometimes examples that reflect a bit more the Latin American way. 

Thanks for your comment.

Un saludo