I've stumbled across this a few times in the past couple years for different reasons. https://johnpierceesq.com/do-you-have-to-register-for-itar-if-you-are-only-manufacturing-ar-15-uppers/

I rely on Pierce's blog with a grain of salt, but largely feel he knows his state law, and I'm in PA so his advice is usually applicable. But this article on the federal level seems off.
The quote regarding "components, parts ..." looks to apply to directed energy weapons.

The language of "(a) through (g)" only pops up once in the list, and not where the blog says it should be. I know that earlier this year the long-awaited reforms for smaller manufacturers finally landed, so I'm supposing things have changed, rather than John being incorrect.

But I don't know that for sure. Specifically, I'm curious about ITAR's feelings on producing drop-in slide rails for Polymer80 Glock compatibles.
And after reading the article again, I'm also curious about ITAR and parts in general. If I produce and innovative FCG to make an M&P's trigger pull like a Canik's, do I need an ITAR certified manufacturer to produce it?

Are slide rails and FCGs even in the same bucket?

Citations with context appreciated. Thank you.

There were major changes to the USML a couple months ago, I am still digesting it. Almost any article written prior to these changes needs to be re-evaluated to see if it was superceded. Most S/A stuff was removed

https://www.ar15.com/forums/armory/ITAR-Final-Rule/44-506797/

The 'adjustment' to ITAR registration apparently failed
the last time around to be passed.
When I have some spare time I intend to go back and
read all the ITAR Regulations from Department of State.

The old rules required ITAR registration if you made ANY  firearm related parts in the USE.
Since YOU cannot control their export it was a true CF.
A couple thousand A year to register.