Woocommerce product editor does not add br

Try editing in the ‘text’ editor and adding   on the empty lines and see if that gets stripped out.

Update:
Here’s a screen capture, yeah it gets stripped out because of WordPress’ default formatting (wpautop), but it still registers what was intended. Here’s the text:

Now here’s the end result on the front end:

There must be something stripping out your formatting either from the theme or some plugin.