As in Below Digram,
Link Connected to N2k is a Normal Port channel , but i beleive in this particular Digram it exhibits Active and standy , i think its end host unsupportive of Normal Prot channel to N5K , do let me know if i am correct or wrong.
There is no problem having direct port channel from End Host/Server to N5k. But from DC Design standpoint, N5K is End of Row switch and Nexus 2k is Top of rack switch to simplfy the design and to reduce cable run and management points.
Now coming back to diagram, there are multiple ways to accomplish redundancy in network when it comes to VPC topologies. For example your each 2k can be single homed with 5k and than you can have vpc from 2k down to Server. You can also have VPC between 5k and 2k and another vpc from 2k down to Server which is called Enhanced VPC.
But keep in mind when it comes to VPC, the feature has lot to do with Hardware and software requirements and that decides which VPC topologies will be supported vs not supported.
I've seen similar when the Nexus is configured for LACP and the host is configured for (on). Nexus (left) can accept the packets with a channel header, since channeling is configured (though inactive). Nexus (right) puts the ports into a down state to avoid vPC inconsistency, as LACP isn't happy on the left side and the Nexus isn't sending channeled packets to the host. But that's just one scenario.
In this particular drawing it is indeed active/standby. But you could also run active/active to the N2k or N5K.
There are several valid designs. Here is a good document, it talks about a lot of other things, but can give you an idea:
I am just wondering if we can combine port-channel NIC teaming and active/standby NIC teaming on server like depicted in the diagram of OP post? [^o)]
Thanks for sharing.