Lava Lamp Freak
macrumors 68000
hmmm. it's there for me. using the stock launcer, long press the home screen and choose settings. it's under the "change icon shape" setting near the very bottom. I do have developer options enabled but not sure that matters.
I don't have this option to Change Icon Shape on my Verizon Pixel 2. Everything else looks the same, though. Very odd.