In Exodus 34:6-7 it is written
וַיַּעֲבֹר יְהוָה עַל־פָּנָיו וַיִּקְרָא יְהוָה יְהוָה אֵל רַחוּם וְחַנּוּן אֶרֶךְ אַפַּיִם וְרַב־חֶסֶד וֶאֱמֶת: נֹצֵר חֶסֶד לָאֲלָפִים נֹשֵׂא עָוֺן וָפֶשַׁע וְחַטָּאָה וְנַקֵּה לֹא יְנַקֶּה פֹּקֵד עֲוֺן אָבוֹת עַל־בָּנִים וְעַל־בְּנֵי בָנִים עַל־שִׁלֵּשִׁים וְעַל־רִבֵּעִים׃
And the Lord passed before him and proclaimed: Lord, Lord, benevolent God, Who is compassionate and gracious, slow to anger and abundant in loving kindness and truth, preserving loving kindness for thousands, forgiving iniquity and transgression and sin; yet He does not completely clear [of sin] He visits the iniquity of parents on children and children's children, to the third and fourth generations.
It says that G-d forgives iniquity and transgression and sin, 3 different things. Yet it goes on to state that only the iniquity of the parents are passed along to the next 4 generations.
Is there any significance in the fact that the transgressions and sins of the parents are not also visited upon these 4 generations?