Well, you must remember how manuals are written, and by whom. It's not the engineers that designed the gear, or even their secretaries or interns. It's the job of technical copywriters, most of who are ESL. But then the engineers are ESL too, but a different ESL to the copywriters. It's all so terribly telephone gamed. Service Manuals tend to be written better than Owner Manuals, because those get some vetting. But still, it's a mess.

To get "full quality" (meaning all 400 lines of luma data) from S-VHS, yes, clearly, S-VHS needed. The signal is extracted Y/C, stays on a Y/C path when using s-video (separated video, meaning Y and both C are on separate carrier wires). It's only composited out to the composite/"RCA"/yellow-wire output.

When you play a VHS tape in an S-VHS machine, then it clearly cannot get a "full quality" (400 lines), given how the VHS format is only 240 lines of luma. It actually does output better-than-VHS quality, but only because VHS VCRs are so crappy. What outputs from most VHS VCRs is not full quality VHS, not even a "full composite quality" in most cases.

The manuals do not state much of this, because it's trivia to the user, and semi-unnecessary video theory to the grunts repairing units.

Most S-VHS VCRs did not record to VHS tapes (without melt/drill hacks, later the "ET" feature), and for that reason VHS really was not mentioned. Remember, "VCR" = video cassette recorder, and these were specifically S-VHS units. It's sort of like discussing the towing ability of a Ford Taurus. That wasn't the intended use, so it's just not discussed in the manual. It's also simply one less legal issue to be responsible for.

Chroma is the same bandwidth on VHS and S-VHS.

What amazes me about this entire situation is that it's spelled out in countless documents, going back decades -- something he admits! But his attitude is "everybody is wrong but me, and has been for 40 years". Right, sure, okay, whatever, no.

Service manuals are a set of instructions on how to do the scheduled maintenance properly for a given machine and how to conduct specific tests as well as parts breakdowns and part numbers and values, They help techs do the service and basic checks. They are not repair guides by any mean, a tech would still need hands on experience to tackle complex repairs, the service manual does not tell you what's wrong with the machine or how it works. Though JVC and I believe Panasonic did release some books describing their VCR technology and enhancements over the years, but those are neither service manuals nor user manuals.