After the weekend's debacle over the expired certificates, I noticed that even though PureBrowser had the options greyed out regarding "Allow Firefox to install and run studies", when I clicked on "View Firefox studies" I could see the workaround fix had already been installed automatically, indicating that despite the setting being unavailable, the feature is still enabled.
Looking further in about:config, I could see that Normandy was enabled:
app.normandy.enabled
IMO this should be disabled by default in PureBrowser, to better align with PureOS and Purism's mission and protecting the users from unintended consequences
Even though in this case Mozilla was being helpful with it, it still feels dirty --- more over I still had to manually apply the XPI fix myself even if it was already pullled by the studies, so I'm not sure how much of this feature is enabled or disabled un PureBrowser.