There ARE Eurorack modules that can standard-shift from Korg's standard to Euro and vice-versa, though.
Fact is, this is a bit of a throwback to the "bad ol' days" where there WERE a lot of different interfacing standards. Korg and Yamaha both used the Hz/V and negative trigger/gate standard, EML had their 1/12V steps, Moog had the awful, rotten, ROT-TEN S-trigger system, and things like the Buchla 100 were off in wackyland, with no real scaling and two different signal paths for audio and control signals. When MIDI came along, some of this was still going on...and remained as an annoying "latency" for those using the older gear. That we have to deal with these NOW is due to either exact replication (Korg's redux of the MS-20, or EMW's rework of the EML 200/300) or outright copying with no foresight to correcting these shortcomings (Behringer's you-name-it).
Do yourself a favor though, and grab an MS-20 mini on the used market (where there's plenty). Be careful to NOT buy an MS-20ic, though, as those were just gimmicky controllers for a software analog emulation system Korg kicked out many years back, and some unscrupulous/ignorant sellers try and foist these off as MS-20 minis. Look for the BLACK nut around the phones jack; the ic has a silver one. Anyway, even with the voltage standard issues, the MS-20 (of any sort) is a real face-ripper! It's hard to say what's the most fun about it, too...the VCF pair? The input section (drum machine + that = instant Aphex Twin!)? The fubar patching routings? Really, it's a fun little box, not to be idly dismissed. But do get the real thing; a lot of the point of that synth DOES depend on its form factor, which still works at 81% size.