The actual tips, like the pointy needle ends of the metal part of the probes dont often have corrosion on them, but the sides of them can. So if you touched the tips, meaning just the metal parts, shaft to shaft it'd read pretty high. However if you touched the slip rings with just the pointy tips of the tips of the probes you're not getting that latent resistance you read from the shafts of the probes that dont actually ever touch anything.
