"All upstream Scope 3, is really someone else’s Scope 1 and Scope 2"

There is a really big problem with this line of thinking about carbon emissions

To start with, The Greenhouse Gas Protocol defines Scope 1 and Scope 2 emissions as those coming from your own operations

https://ghgprotocol.org/sites/default/files/standards/Scope3_Calculation_Guidance_0.pdf

Scope 3 emissions come from your value chain.

The key word here is 'your' value chain

If you put in motion the process to conceptualise, design, test and scale production of a product to sell to your customers you are the *point of origin* for the entire product

The unit of record here is the product itself, not the myriad of components and sub assemblies

You can't put the responsibility for the emissions that come from the product you want to make onto the suppliers within your value chain who are delivering what you need

This isn't to say that every supplier in every tier of a value chain doesn't have their own responsibility to reduce their emissions to the absolute minimum, but...

If you are the *point of origin* for a product then you can and should put in stringent requirements around emissions into your Service Level Agreements with suppliers - especially long term, strategic suppliers

The ultimate responsibility has to reside with the *point of origin* in the value chain, otherwise the danger is the 'responsibility' for emissions is passed backwards and forwards throughout often large, complex value chains

A kind of 'carbon gerrymandering' happens where the boundaries of where the emissions sit are altered to be most advantageous for whoever is doing the reporting