> i have yet to see any service provider use BGP confederation in production.
There are at least 26 publicly visible routes on IPv6 that have visible confederation in them.
Maybe the best/worst example is 2402:8100::/32 ( https://bgp.tools/prefix/2402:8100::/32 ) :
# birdc s ro 2402:8100::/32 all
BIRD 2.15.1 ready.
Table master6:
2402:8100::/32 unicast [transit6_orange 13:42:56.368] * (100) [i]
via xxx on xx
Type: BGP univ
BGP.origin: IGP
BGP.as_path: 5511 3356 55644 {36040 38266 45271 55410}