Favorite flat mount dropouts?

Question related to Flat Mount.
Both the SRAM and Shimano tech documents specify that the mounting thickness should be at least 10mm. Seems a bit overkill to me for steel or Ti frames and I’m thinking it’s more related to carbonium.

Considering there are Post Mount to Flat Mount adapters from A.S. Solutions and Wolftooth that are significantly thinner than that, you’d think it would be fine to slim it down a bit.

What are your thoughts about this?