On desktop printers, ink being deposited on the far left platen foam is normal. I've never understood why these printers do this as part of the cleaning routine, but apparently it's normal. It's been discussed here before. IIRC, with OEM carts, the ink deposits tend to be in fairly well-defined lines. With refillables, it's not as well-defined, which I have assumed is because they're a simpler design without all the micro-venting that the OEM carts have, and so more ink is being let out during this process. However ... if this area is very wet, then that's a sign of a leaking cart. Some carts will leak a little when first inserted, but if a lot of ink continues to be deposited there, then I'd be suspicious of one or more of the carts (speaking from experience). This leaky cart issue won't apply to an R3000, as it has ink lines and dampers, and it's the dampers not the carts that prevent the ink from draining.
The large format printers apparently don't have this far left foam. My 3880 has a plastic lid there. Because these printers have maintenance tanks rather than waste pads, my hunch is that they're doing the same thing, but that plastic lid pops up so that the ink discharged there drains to the maintenance tank. I have no proof of this, but it appears to me that there's something under that lid.
The R3000 sits in no mans land - between the desktops and the pro printers. It has ink lines and dampers, but no maintenance tank. So while I've never used one, it sounds like it's more like a desktop in terms of the left side platen foam. But that doesn't answer the question about why waste ink from the MK/PK switch. Don't forget that more ink is used in one direction of the switch than the other (I assume that the R3000 is the same as the R3880 in this respect), so you should see more ink going into the waste bottle in one direction of the switch compared to the other.