Is such accuracy even needed?

That seems to be the case. A few games will break using stock (official spec) speeds:
- American Tail: Fievel Goes West
- Breath of Fire 2: German vocal intro
- Clayfighters supposedly has sound skip issues
- Earthworm Jim 2: European sound effects

Running the S-SMP at 32040*768hz instead of 32000*768hz fixes everything, except R. Belmont is saying there's still some slight issues with Clayfighters.

The first two break if you change CPU<>SMP skew by 768hz more than what I use now.

Off the shelf crystal resonator will have about 50ppm initial skew.

S-SMP stock is 24576000hz. Clocked at 24606720hz. That's a skew of 30720hz. Which is closer to 1,000ppm skew. In fact, almost all SNES units we've clocked have ended up right around the latter. It seems more like the spec was wrong than all the crystals.

That would mean the game requiring very precise timing would not work on that particular piece of hardware... In that case you can claim to emulate said kind of unit and explain it not working is normal behaviour

I try and explain this, but people assume that because it worked on at least one SNES, that emulators are flawed if they don't also run it.

There are really flat out *broken* commercial games out there. Death Brade/Blade and this European racer won't work unless you initialize WRAM to non-0x00s. It checks a certain byte without initializing it, and if it's zero, the game doesn't work. Given the variable nature of DRAM on power-on, there's probably a 1:256 chance that will be the case on the real thing.

So, if we know console X can run these titles, and we match its oscillators, then we can rule out clock issues if the games still break in emulation.