In short, no.

Halo sales occur if someone clicks on an ad for product A but then buys product B instead.

For example, two products are part of a single listing. Product A has higher ad spend, which means most paid search customers arrive at the listing via product A's ad spend. If some customers then buy product B instead of product A, the CAC will still be attributed to product A. In our experience, this doesn't occur often and should not affect the overall conclusions from the insights.