This may be true of publisher in-house development teams, but I've seen and worked at third party studios that do little to nothing about post-release archival,

This may be true of publisher in-house development teams, but I've seen and worked at third party studios that do little to nothing about post-release archival, a fact connected to having minimal IT controls and the end of a project often resulting in a massive layoff. Things get lost in the dust-up; dev kits get lent out from a publisher for one project and then aren't returned. The build server gets "reused". The same version control repo is used to ship two different games sharing the same engine. One coder stays behind after the rest of the team has been let go or moved to something else, in order to fix bugs, so he's the only one with the most up-to-date build. What is left over is a mishmash of project artifacts but no guarantee that "project K at point in time T" can be reconstructed in full. And with some of those Sierra projects, their archival might have all the assets they could find; that doesn't mean they have all the assets.