Let’s cut through the confusion. The version number refers to the native macOS client , not the web app or the iPhone app. If you are currently using the old "WhatsApp Web" saved as a Chrome app, you are running a different codebase.

, you can still keep the conversation going on your High Sierra (10.13.6) machine. The Reality Check: Official Support

If you are running this version (or have been prompted to update), here is a breakdown of what 10136 brings to the table, why it matters, and what you should watch out for.