This is complete and utter garbage.
I am happy to discuss this with you, directly and I suggest you join the list for the Advanced Pilot Seminars class that myself and Andrew Denyer run here. This is the class started by GAMI and John Deakin.
As much as this sounds cocky, nobody in Australia has done more with Dyno testing of the unleaded avgas G100Ul than me, so I know a few things about this topic.
The sooner we get TEL out of Avgas the better. The USA spec fuel is identical to ours. Mostly 100LL.
I assume John-Paul Townsend at GAMI replied to you. He would be 100% correct.
LAME’s are well meaning but are not qualified to comment any more than your cat. Sounds harsh but it is true.
You can email me at firstname.lastname@example.org and I will happily help you out.