Hello Laz,
I understand that 2001:DB8:1234:AB80::/57 is the “optimal” summary of 2001:DB8:1234:ABA2::/64 and 2001:DB8:1234:ABC3::/64. but I see that this summary includes the whole pool [2001:0db8:1234:ab80:0000:0000:0000:0000 - 2001:0db8:1234:abff:ffff:ffff:ffff:ffff] … which must be specified in the Lan documentation.
Then, if there is no constraint in the exibit asking to exclude everything before 2001:db8:1234:ab7f:ffff:ffff:ffff:ffff and everything after 2001:0db8:1234:ac00:0000:0000:0000:0000 I thinks that an “industrial” summary can be 2001:DB8:1234:AB00::/56 (pool from AB00 to ABFF) or, even more , 2001:DB8:1234:AA00::/55. then, with a good industrial IP hierarchical organization (but expensive in IP), no Lan documentation should be made.
(I think, for example, a question from the ccna that poses "is 2001:db8:1234:aa00 : 55 a possible summary of 2001:DB8:1234:ABA2 : 64 and 2001:DB8:1234:ABC3 : 64)
Am I right ?