SMB MultiChannel only sees one server-side NIC? Both client and server has 2 NICs each on same subnet, 4 IP addresses

The client is Win 11 PC. The server is Synology DS1821+.

Running Get-SmbMultichannelConnection returns the following on the client:

Shows 2 SMB MultiChannel connections, source is the 2 client NICs but target is only 1 server NIC

File transfers though SMB will correctly be load split between the 2 client NICs but will cap out at 10 Gb/s due to only 1 server NIC being visible.

The machines are connected through 2 subnets. The management / internet subnet is 192.168.1.x, and the subnet intended for SMB is 192.168.2.x

The management subnet goes through an ubiquiti UDM Pro. The SMB subnet is switched by a Ubiquiti Aggregation Switch. Only the 2 clients in question and 4 NICs are connected to the switch and the second subnet.

192.168.1.150 is a private DNS hosted by the NAS to resolve some local custom domains not related to SMB.

All 4 SFP+ NICs have been set up for MTU 9000 Jumbo frames. Whereas both of the management ethernet NICs are on MTU 1500.

Synology NAS:
(Ethernet)
   IP: 192.168.1.150
   Gateway: 192.168.1.1
   DNS: 192.168.1.150

(SFP+ 1)
   IP: 192.168.2.151
   Gateway: 192.168.2.1
   DNS: 192.168.2.1

(SFP+ 2)
   IP: 192.168.2.152
   Gateway: 192.168.2.1
   DNS: 192.168.2.1

Win 11 PC:
(Ethernet)
   IP: 192.168.1.11
   Gateway: 192.168.1.1
   DNS: 192.168.1.150
(SFP+ 1)
   IP: 192.168.2.101
   Gateway: 192.168.2.1
   DNS: 192.168.2.1
(SFP+ 2)
   IP: 192.168.2.102
   Gateway: 192.168.2.1
   DNS: 192.168.2.1