Rise and motion sickness

Rise supports WCAG level AA (https://access.articulate.com/support/article/Rise-360-Supports-Web-Content-Accessibility-Guidelines). The success criterion you are referring to is  SC 2.3.3:
Animation from Interactions which is an AAA standard. Very few tools support natively building AAA-compliant sites (web, e-learning, or otherwise).

I think you have two options here: One is to reply to the complaint stating that your goal is to create Level AA compliant courses. The second option is if the left to right animation of the process interaction is an issue for one of your learners, provide an alternative in the form of an accordion interaction or the Timeline block (personally I would probably use Accordion since the Timeline might be pretty long). You can call out in a text block that the same content is contained in both the accordion and the process and learners can choose which one they'd like to use.