I can't say whether it was a mistake on the level of being unintentional, but I do think it was a mistake on the level of being an unwise decision in the event that it wasn't unintentional. There are probably a lot of people going through this course who have no idea Hungarian even has definite conjugations, in which case this sentence would be really confusing. :/
This is one of the more fun things in the Hungarian language. There are two modes of conjugation, generally called 'indefinite' and 'definite'. What you have learnt so far was the indefinite conjugation. That is always used if the verb in a sentence doesn't have a direct object (-t word) or the direct object is not a certain one (like 'a table' or 'a red house').
Látod is the 2nd person singular definite conjugation of lát. It is used here because you're seeing a certain group of windows, the windows, az ablakokat. Definite conjugation forms are used if the direct object is preceded by the definite article a, mostly, or if the object is ezt or azt (this or that). There are some other indicators but those aren't important for now.
The conjugation forms for Ön and Önök are the same you'd use for ő and ők, respectively. Namely, 3rd person singular or plural forms.
Ah, then "Az az ablak?". "Az az" is actually pretty common. Whenever stating "That" or "This" + Noun, you can't simply say "Az" or "Ez" + Noun, you need to insert the definite article, which means that in some cases you end up using both "Az" for "That" and "Az" as the definite article, for example:
Az az új autó nem annyira jó - That new car isn't so good
Note that this is also the case in the plural:
Azok az új autók nem annyira jók - Those new cars aren't so good