FaceType

You are correct. But the letter ‘I’ never has crossbars, no matter what font you are looking at. If you mean the horizontal stem, that is a serif.

In sans-serif text typefaces capital ‘I’ is traditionally a simple vertical rectangle without serifs. But we were estimating some folks would miss those serifs so if you want to have a ‘properly-formed’ capital ‘I’ just activate stylistic set 02 (ss02, = ‘Alt I J i j r’). To see what this looks like, take a look here: https://www.monolisa.dev/tester/text

Activating stylistic set 01 (= script variant) does not effect the look of figures. You can try it out here on our website: https://www.monolisa.dev/tester/code