The interlacing always gets messed with in these PAL/NTSC conversions. It's a very primitive lossy conversion method from the 80s/90s. Zero advancements in hardware PAL/NTSC conversion was made this century in consumer VCRs and DVD recorders. Even "high-end" on-the-fly conversion from the likes of Faroujda, Ektron, etc, all still sucked.

Proper conversion requires non-live (non-linear) slow separation of "larger than frame" chunks. You need to extract all fields, anti-alias as needed, resize or re-color, and it's slow. Even now, in the 2020s, it's a process. I know, because I sometimes do it. Because it is such a process/PITA, I mostly just do it for personal projects --- meaning I won't even do it for paid work.

Video isn't as easy as some people want to think. It's not a trivial matter of plugging in something bought from eBay, Amazon, Walmart/Asda, etc, unless you don't care how bad it looks. Most people don't accept what is now known as "potato quality" video. They already want HD and 4K, so we'd better not screw up low-end SD VHS/DVD.

I think I know where the confusion is.
lordsmurf, there is absolutely NO PAL<->NTSC conversion in this scenario.
NTSC tape is used in PAL VCR. It doesn't convert it to PAL. It just plays it as is.
PAL tapes are not converted to NTSC. They will be played as PAL. Period.

I think I remember reading some DVD recorders did both native NTSC-NTSC and PAL-PAL passthrough, But the recommended ones such as the Panasonic ES-10/15 and their European counterparts did not as far as I know, I think that's what LS is talking about.

Correct.

Actually, DMR-ES10 PAL is one of the few with that feature. NTSC>NTSC, PAL>PAL, no conversion.

NTSC tape in PAL VCR is converted/output to PAL60. It does not output native NTSC.

Not that few. There are many like that. And I have one - Sony RDR-GX350.
That alone just confirms PAL VCR can read NTSC tapes.
But again, that conversion to PAL60 is implemented in UK models.
EU models output standard NTSC signal. I have 3 such units. Do you want the model numbers?

The JVC HR-S7600AM VCR I have plays NTSC tapes in native NTSC and PAL tapes in native PAL, It can convert however if you change the output format, but only to PAL60 or NTSC 4.43, it does not convert PAL to NTSC or vise versa.

Well, yeah, that's the rare AM. That was one of the selling features.
Not PAL-only E, EU, EK.

And there is Panasonic NV-W1 (AG-W1 in US) what is able to play all formats, including SECAM etc in native format or to convert between them. Sadly it has no S-Video output and line TBC, so in those rare cases when I need to record something from SECAM (with converting to PAL of course) or NTSC (without converting) I use it with ES10 what supports both PAL-PAL and NTSC-NTSC.
Otherwise NV-W1 quality is decent. If they had made a s-vhs deck like that... ;)

Samsung, Panasonic, JVC, Aiwa, Toshiba and other brands made multi-standard VCRs that can playback and output the native format of 2 or 3 color standards in addition to the conversion, some of them high end S-VHS, others are just basic VHS, but I think the discussion here is about DVD recorders.