Steps to reproduce:
1. Open https://jsbin.com/dabetaq/edit?css,output
All three boxes should have the same, correct text slant.
In Safari, the slant is incorrect for the second and third box.
It appears that font-style: oblique only renders the correct slant if the upper angle in the font-style descriptor is at least 20deg in Safari. But the variable font has a 'slnt' axis range of 0 to 10*, which translates to the CSS range 0dge 10deg.
*You can check the font file’s 'slnt' range on wakamaifondue.com.
If you change this range to 0deg 20deg, Safari renders the slant correctly. Safari should let authors specify the variable font’s actual slant range. Currently, authors have to use 20deg as some sort of magic number to get correct rendering in Safari.
Note: I’m not an expert on variable fonts, but the range 0deg 10deg works in Chrome and Safari, so this seems to be a bug in Safari.