Hello Jonathan!
Please allow me to suggest some corrections for some of your points.
First, American Society for Testing and Materials (ASTM) is far more than just a, “…commercial consensus spec” provider. ASTM is an example of the institutionalization of American scientific standards that distinguishes us from countries like China. Perhaps if you actually read one of these “specs” you would realize that they are far more than just some commercial consensus.
Second, if you are going to pick a specification to read, may I suggest you go with ASTM D910-20. You will find that it very specifically provides “build standards” for LEADED avgas - specifically, 100LL.
Third, Swift Fuels UL94 is an unleaded avgas using the “build standard” ASTM D7547-Grade UL94, not ASTM D910. It is an unleaded avgas of 94 aviation octane (as distinguished from automotive which is an average of RON and MON). Aircraft engines requiring 100 octane for safe operation should not use UL94.
Finally, the most significant point I can offer you here is that there is no ASTM standard (yet) for 100 octane unleaded avgas. ASTM 7719 is a purchasing (only) specification for 100 octane unleaded avgas, not a build standard.
I totally agree with the main thrust of your comments about GAMI’s STC. Essentially, G100UL that you will be able to put in your airplane soon was completely developed - finished - by 2013. The time between then and whenever it is actually being pumped has been consumed by politics and redundant, combative FAA demands for testing. Most of the tests were done more than once. GAMI has earned the right to recover some of their investment by charging for their STC.