While you're correct that the last two digits also lead to the correct answer, that may not have been the case. For example, if the last digits of the two numbers were 72 and 16, the produce of the units digits is 12 while the last two digits of the product when taking into consideration both the units and tens digits is 52. For that reason, it's best to follow the method outlined in the explanation video in this case :)
2 Explanations