I've had Thinkpads with backlit keys that still had functional drain holes. I know because they were used a few times.

Transparent silicone exists so I don't see why it would be a problem

I must be imagining that I destroyed an older Thinkpad keyboard with a spill.

You can destroy the keyboard but they're replaceable and usually contained the spill to just the keyboard so it didn't damage any of the more expensive components like the main board. The goal wasn't an invulnerable keyboard but to limit the damage to a cheap replaceable subcomponent that kept the laptop alive.

Man I've been using MacBookPros for so long I forgot how many greebles laptops used to have on the bottom.