Canyon Ultimate: Downtube Hole?

Weird question but I just got my Canyon Ultimate (which, after 4 hours or so, may be the best bike I’ve ever ridden). But there’s this quite obvious hole between the two bolts for the water bottle cage on the downtube, with some sort of plastic widget in it. It’s clearly not waterproof, and I’m worried when I ride in the rain, drops of water will get in there and never dry out.

I’m guessing this hole has something to do with accessing cables (or wires, but I don’t have electronic shifting). But shouldn’t the covering there be a gasket of some sort? Or should I not worry about it?

Googled around, couldn’t find anything.

I have a Canyon CX bike and have the same hole with a plastic cap, not sure either.

I have a similar hole on my Tarmac although mine is plugged with a little rubber bung and seems watertight enough.

I presumed it was a cable port for internally routing your Di2 front derailleur cable.

I’ve read online it’s how the hold cables snug inside frame to keep cable rattle away
.