"Gold-plated connectors" are a common snake-oil in audio electronics. The only benefit it provides is that it doesn't tarnish like copper would. Gold is a worse conductor than copper and it's very soft and brittle. With pieces that are constantly making contact that plating is likely to wear away quickly. You only need it your contact is exposed to air anyway, and then if it is you really need the whole thing to be gold-plated. Also, you'd better have some nickel on between the gold & copper.
Ah, yes, I agree that it doesn't make a lick of difference for audio connectors and that advertising gold plating is just a way to jack up the price. For this type of mechanical switch, though, I don't think the copper oxidation would wear away since it's a very light touch and there is very little rubbing movement, just blunt contact. Also, I'm pretty sure that there would be no incentive for companies like Matias to offer gold plating if it weren't really needed - it's just an extra expense and the high-end mechanical switch market is basically nonexistent compared to the high-end audio market.
If I understand things correctly, anyway.