A/B Testing and SEO concerns

Hello there,

A client of mine A/B tests and I don't believe they are following best practices but would like to clear a few things up before I provide recommendations.

Their B page will have a slightly different URL, for example:

Page A (www.example.com.) Page B (www.example.com/test1)

At this moment and time, they place Page B under their robots.txt file; however, Page B's canonical tag is www.example.com/test1. I understand they need to change their canonical tag to always point to the primary page (Page A) and avoid placing Page B in their robots.txt file.

However, I need to explain what the dangers are of placing their Page B testing page in their robots.txt file, rather than just canonicalising.

From what I understand, there is a risk that the testing page could be indexed by Google if the page accumulates links, which could then lead to duplicate pages existing in Google? Furthermore, any link equity established from Page B will not be spread to other pages on the site, as Page B resides in the robots.txt file?

Are there other signals apart from links that could result in Google indexing the page such as a large amount of traffic?

Also, since testing page B has a different URL, will the traffic equity garnered from Page B benefit Page A, or solely support Page B?

Thanks