I'm playing Minecraft 1.16.3 on MacOS and using a Logitech mouse with smooth scrolling enabled in Logitech Options.
When scrolling through the Hotbar, one "tick" of the scroll wheel will scroll through multiple items, instead of just one like the intended behavior.
This issue was reported before in MC-123773 and the described solution was to enable discrete scrolling and set scroll sensitivity to 1, but that solution no longer works.
Disabling smooth scrolling in Logitech Options will solve this issue, but the solution provided in MC-123773 should have fixed the scrolling issue without necessitating this approach. I also cannot set a custom profile for Minecraft in Logi Options because the instance of Minecraft does not run in .app format.
In short, the solution prescribed in MC-123773 to fix Hotbar scrolling to the correct "1-item-per-tick" behavior no longer works.
Please also report this to Logitech, as it may be an issue with their software/drivers.