Why does BAP unicast client have to have more than one sink or source?

[yclistanford]

https://github.com/zephyrproject-rtos/zephyr/blame/60835568fce74b9e3e752f2ec139d6e31b41a4b5/subsys/bluetooth/audio/bap_unicast_client.c#L60

I'm not sure why this check is needed. I read table 4.1 and 4.2 in BAP spec v1.0.1 at https://www.bluetooth.com/specifications/specs/html/?src=16212-BAP-html5/out/en/index-en.html#UUID-e610da3a-d737-b38e-7302-6c9e934a99f6, and I still don't understand why a unicast client has to have either zero or >1 endpoints in each direction. Can someone help?

If this is not required by the spec, this check just adds inconvenience to development.