A really interesting article Kent, thanks for sharing.
It looks like it works to me ")
You aren't stupid at all... They are still not welding aluminum to austenitic stainless :)
I think the key thing for guys like you and I to understand is that what they have accomplished is sort of a "multi-process" joint, in that the Aluminum is welded and the stainless is brazed (solid state).
"The Welding-Brazing Lap Joints are obtained by melting the aluminum alloy and
forming a connection with the SS with solid state through wetting and interfacial reaction." {Emphasis mine).
The Macros show what the quote states.
How this type of connection would be used is also a good question... I suppose a next step would be to continue trials that look at the Aluminum's long term aging and galvanic reactions along the faying surfaces... (how does the metallic joining hold up under various service conditions..
Macros and quote clipped from:
https://www.researchgate.net/publication/282397025_Effect_of_torch_position_and_angle_on_welding_quality_and_welding_process_stability_in_Pulse_on_Pulse_MIG_welding-brazing_of_aluminum_alloy_to_stainless_steel