Absolutely correct. A UX designer will have the stake at the table with all sorts of decisions that impact the user experience.

For example:

Two competing microservices? One has a spin up time of 0.3 secs, the other 1 sec. The first is two times the price. It is the job of the UX designer to understand the impact of the longer spin up time to understand if it would impact the user experience.

The UX designer then works with the Product Manager to build a business case for the correct service and thus you've made a decision that impacts the UX but is not a UI or interaction based conversation.