I largely agree with your points, especially about 4-up reconstruction.
> variation in CRTs was very high back in the day
I wanted to add some more info around this point. In cases of home consoles this is true (because they hooked up to whatever TV you had) but there's one very large case where it's not true - and it's a case that matters quite a bit, especially from a historical preservation perspective.
Most arcade cabinets were made on factory assembly lines and used bare industrial CRTs. These CRTs were made by a handful of companies and arcade manufacturers selected the CRT model for a game by its specifications, which often differed from CRTs designed for use in consumer TVs. We know exactly which CRT (or CRTs) were used in most arcade cabinets and the detailed manufacturer specifications and schematics for those CRTs are preserved and online. When researching the proper modeline frequencies to set my quad-sync monitor to (because it's a chameleon), I look up the specifications of the original CRT in the original cabinet. The game developers usually had one of these industrial CRTs on their desk, so that they were developing for the exact CRT that would be in their game's arcade cabinet.
But it's even more precise than that. Many game ROMs have a set of hidden factory calibration screens with alignment grids and color bars. On the manufacturer's assembly line, after installing and connecting the CRT, workers fired up the game, went into these screens and adjusted the internal controls of the CRT so the horizontal & vertical positions and sizes of the grids were correct as well as the color bars via the tint control. I use these calibration screens to this day to properly set up my CRT to match the adjustments of the CRTs in the original cabinets (which the game ROM was written and tested against). Because my monitor handles so many ranges of frequencies, it stores and recalls these horiz/vert/tint adjustments for each unique scanning frequency (along with other adjustments like pincushion, skew, bow, etc). Historians have even managed to preserve some of the instruction sheets written for the factory floor workers to use when adjusting the CRTs to the intended spec.
Fun photo of the Ms. Pacman assembly line: https://thedoteaters.com/tde/wp-content/uploads/2013/03/pac-...
