The background matching introduced into pipe_tasks a couple of years ago works only on drift-scan observations and is not applicable to pointed observations (e.g., DECam, HSC, LSST). Making background matching work with pointed observations will take a lot more care and coordinated processing across patches due to the smaller scales involved (arcminutes for CCDs vs many tens of degrees for SDSS runs). However, background matching is currently enabled by default in the stack, which necessitates overrides (which are often neglected, at least initially, by the new user) for pointed observations, which is the vast majority of current use cases.
Given that the current background matching code is only applicable to a single camera supported in our stack,
we have agreed to remove it and disable MakeCoaddTempExpConfig.bgSubtracted by default.