"I feel like I stepped into a hornet's nest"
That's too bad, as I've had the same oil change experience. Many have. I personally sucked out some of the stinkiest, nastiest, stickiest oil I've ever encountered out of my 7.3's HPOP reservoir, particularly off the bottom (currently 196k, I've performed all my own oil changes for the last 40k miles of it's life). That stuff smelled as though it had been in there since the Jimmy Carter administration. It might be a case of the lower third of the reservoir not getting any circulation, and the oil in the heads, that pushes on the injectors, gets returned at a very slow rate. I dunno. I used Bill Hewitt's change method, suck the reservoir dry, refill with clean oil, rinse and repeat to get most of the oil that is in the cylinder head galleys.
Mine also ran noticeably smoother afterward. It ran smoother not because I wanted to justify my extra labor, but because it does.
Some guys across the forums argue "Ford says it's not necessary, so it must not be..." or "I'm a Ford trained technician, we never do this" and then there's those who proclaim "snake oil and ****************". You go, cowboy! I'm old enough to just laugh at that. My eyes and nose tell a different tale.
They can swap worn out injectors at 170k or 220k, it's a free country and your money/time.
As for myself, I'll do a little more maintenance on my rig to hopefully put off the several thousand dollar, PITA activity, particularly on a 7.3 van.