When I translate this with other programs and ask native speakers, this is completely incorrect.

Question

My research tells me that he visto means I have seen, NOT I saw.  Maybe this is correct in some countries, but I haven't found any native speaker in the U.S.A. who translates these simple past sentences (i.e. I saw, they saw) with the use of haber.  They are simply vi, viste, vio, vimos, and vieron.

Answer

Hi David - currently, Kwiziq focuses on European Spanish though we hope to be able to include the various American dialects too. For the most part, the differences are quite minor (comparable to British English versus American English) but the use of the present perfect and preterite is one area where there is an important difference.
I'll get one of our linguists to answer in more detail, but I know that the preterite tends to be used in Latin American Spanish where we would use the present perfect over here in Europe.
However, this lesson is really about conjugation, not usage, and the hint in testquestions will remind you which tense to conjugate so don't have to worry too much about the English.
Hope that helps!

Answer

FYI this lesson explains how the two tenses are used in European Spanish (there's a note explaining that the rules are different for the American Spanishes):
https://spanish.kwiziq.com/revision/grammar/when-to-use-el-preterito-perfecto-or-el-preterito-indefinido