I cannot speak for all studios, but organising playtests at DICE is a tech-skill heavy activity. We do playtests 2 times per day, 1 hour per playtest.
This requires the person that organises the playtest to chase all stakeholders of a playtest to ensure that their changes are in the branch before the playtest, and their changes have been verified to work. To chase issues and make sure those issues are fixed by others, or fix the issues themselves (often times complete blockers that require design, art, or backend changes), build the game, deploy builds, use tools to spread those builds across the studio, get servers up and manage those servers during the playtests, gather feedback, react to an amount of real time issues for every single playtest by fixing things on the fly, send that feedback to the affected stakeholders, send playability / stability reports, and all other various tasks.
It may be different for a single player game that rarely gets playtested, or gets playtested based on milestones and what not, but with a studio as big as ours, the playtests are a very involved activity.
We can immediately verify, approve, or disprove designs and changes twice a day, every day.
Based on my experience, people doing UXR usually don't posses these tech skills. Our QA do work with our UXR folks directly though, our playtests basically feed builds directly into our UXR sessions so we get nice comparative feedback between groups of people on the same builds and same experiences quite often.
I would very much like to do a GDC talk on this one day, as we effectively do a "release" twice a day, every day. :D