Unable to render custom ArgsTable

[mkrds]

Describe the bug
After the update from version 5 to 6.x import { PropsTable } from '@storybook/components' component is no longer available and I'm trying to replicate it with the new import { ArgsTable } from "@storybook/addon-docs/blocks" with no luck.

Why do I even need it? Well in our open source component library we have created an util that helps us with documenting props of styled-system package because prop-types that are being spread from another package does not render properly in storybook.

Here's the util:
https://github.com/Sage/carbon/blob/master/.storybook/utils/styled-system-props.js#L468

This util is then used directly in *.mdx files like that:

<StyledSystemProps of={Select} margin />

In SB5 this generated 2 propTables, one for the props defined directly on the component, and the second one which is created manually with the styled-system props.

Expected result of that can be seen at the bottom of this page: https://carbon.sage.com/?path=/docs/design-system-select--controlled

So after updating to SB6 I've done some digging and after finding this comment #11105 (comment)
I tried using the ArgsTable with properly structured rows prop (but without story or component props) to create a custom ArgsTable, but no matter what I do I always end up with No inputs found for this component. Read the docs error message. I even tried copy pasting the code from https://next--storybookjs.netlify.app/official-storybook/?path=/docs/docs-argstable--normal but still I get the same message all the time.

So to sum up:
<ArgsTable of={Component} /> works fine but <ArgsTable rows={...} /> does not in mdx files

To Reproduce
I hope I described it well enough in the section above.

Expected behavior
I'd like to see my custom defined ArgsTable

System
System:
OS: macOS 11.1
CPU: (8) x64 Intel(R) Core(TM) i5-8257U CPU @ 1.40GHz
Binaries:
Node: 12.16.1 - /usr/local/bin/node
Yarn: 1.22.10 - /usr/local/bin/yarn
npm: 6.14.8 - ~/Code/carbon/node_modules/.bin/npm
npmPackages:
@storybook/addon-a11y: ^6.1.18 => 6.1.18
@storybook/addon-actions: ^6.1.18 => 6.1.18
@storybook/addon-docs: ^6.1.18 => 6.1.18
@storybook/addon-google-analytics: ^6.1.18 => 6.1.18
@storybook/addon-knobs: ^6.1.18 => 6.1.18
@storybook/addon-links: ^6.1.18 => 6.1.18
@storybook/addon-viewport: ^6.1.18 => 6.1.18
@storybook/addons: ^6.1.18 => 6.1.18
@storybook/components: ^6.1.18 => 6.1.18
@storybook/react: ^6.1.18 => 6.1.18
@storybook/theming: ^6.1.18 => 6.1.18

[mkrds]

After doing some more digging I've noticed that it actually works, but the ArgsTable has to be imported:
import { ArgsTable } from "@storybook/components"
instead of
import { ArgsTable } from "@storybook/addon-docs/blocks"
to be able to pass other props like rows or error.
Kinda hard to find it in documentation tbh :)

[shilman]

@mkrds those @storybook/components components are undocumented internal APIs subject to change. the doc blocks from @storybook/addon-docs/blocks are the public APIs. Documentation is thin, but will be getting better https://storybook.js.org/docs/react/writing-docs/doc-blocks