ソニーUSAのサイトでも、一応、シーリングしてダストと湿気の影響を最小化している、とは言ってるな。ただし、100%保証しません、とも小さく書いてる。w

ま、ソニーからしたら、「誤解する方が悪い」ってことなんだろ。

Highly durable and operable in tough conditions

The α7R III functions reliably in challenging environments. Its body is fortified by lightweight, high-rigidity magnesium alloy top cover, front cover, internal frame, and rear cover.
The number of lens mount screws has been increased to six for enhanced durability.
Major buttons and dials are sealed. Sealing is provided throughout the body to minimize entry of dust and moisture29.

29 Not guaranteed to be 100% dust- and moisture proof.

https://www.sony.com/electronics/interchangeable-lens-cameras/ilce-7rm3/specifications