Great question — answering as the UphillTech team:
[Edited a few times per comments] Bounce rate and exit rate aren't comparable values. For Page A, the bounce rate is (sessions where the only hit was a Page A PV) / (sessions that landed on Page A) whereas exit rate is (Page A PV that were the last PV of their session) / (all Page A PV) See Exit Rate vs. Bounce Rate from Analytics Help. Since your bounce rate is defined, your cart and checkout pages are getting some landing hits, but if there are not many landings on those pages, the bounce rate isn't particularly meaningful - it could be changed a lot by just a few sessions. Question 1: why are pageviews are getting counted as landings when these shouldn't be landing pages? Is there really...
Full answer by Reve: https://webmasters.stackexchange.com/a/126182 (CC BY-SA 4.0).
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