No, it's not really a "recommended minimum", it's the size of the allocation for a local network segment, and that is because stateless autoconfiguration uses the last 64 bits of the address, and thus doesn't work with smaller subnets - and making the allocation for a local network segment larger doesn't make sense, as autoconfig can't use it anyhow (and you certainly won't have more devices either).
The recommended minimum for "a network" in the sense of an allocation assigned to a different administrative entity is a /56, so that multiple network segments can be set up without any further administrative overhead and without incentivizing network idiocy like NAT that's been holding us back with IPv4 for far too long already. Unfortunately, many providers seem to not have gotten the memo, allocating all kinds of idiotically small networks, thus essentially breaking IPv6 before it even got adopted ...
edit: I guess I should mention that providers themselves tend to get a minimum allocation of a /32 from their NIC, so they can assign 16 million /56 without running out of addresses (at which point the income generated from 16 million customers presumably should be more than enough to pay for another /32). They are simply majorly wasting address space by not allocating it ...
The recommended minimum for "a network" in the sense of an allocation assigned to a different administrative entity is a /56, so that multiple network segments can be set up without any further administrative overhead and without incentivizing network idiocy like NAT that's been holding us back with IPv4 for far too long already. Unfortunately, many providers seem to not have gotten the memo, allocating all kinds of idiotically small networks, thus essentially breaking IPv6 before it even got adopted ...
edit: I guess I should mention that providers themselves tend to get a minimum allocation of a /32 from their NIC, so they can assign 16 million /56 without running out of addresses (at which point the income generated from 16 million customers presumably should be more than enough to pay for another /32). They are simply majorly wasting address space by not allocating it ...