I agree!
This idea for A/B testing forms was submitted on another forum thread in March 2019, and the latest reply in June of 2020 for a community manager indicated that this idea wasn’t on the product team’s roadmap.
It would be an invaluable feature with all the other advacements that the HubSpot platform has made. Added my upvote on both posts in hopes that HubSpot will revisit their consideration.