Nosto hasn’t changed its patented technology with the release of A/B Testing & Optimization. If you want to learn more Nosto & SEO, you can find our general article here: https://help.nosto.com/en/articles/586728-nosto-and-search-engine-optimization
Generally speaking, there is myth that A/B testing would hurt search engine rankings because it could be classified as duplicate content, which search engines don't seem to appreciate.
It has been stated clearly by Google's Matt Cutt that A/B Testing would actually improve the functionality of your site. You can find all information here. Website Optimizer has a good breakdown of the myth too, and why it doesn’t hold up.
If you're still concerned, you can always add a "no index" tag to your variation page. Detailed instructions on adding a “no index” tag can be found here.