USB Dongle on ttyS0 with Hyper-V

Since the acquisition of VMware by Broadcom and the subsequent elimination of ESXi Free, I’ve started moving my entire home network over to Hyper-V. I tried Nutanix Community Edition, which I use professionally, which was OK but there is no option for USB Passthrough. Yes, I understand that Hyper-V doesn’t support traditional USB Passthrough like ESX does.

The Question
Is there something running on ttyS0 in the standard HA installation that would cause a conflict with a device that has been piped to the VM? For full details, read on.

The Setup
HA running on Hyper-V deployed with disk images.

On the Hyper-V host I used Set-VMComPort to add the name pipes.

Set-VMComPort -VMName haos -Number 1 -Path \\.\pipe\COM4 -Passthru # Used for Zigbee
Set-VMComPort -VMName haos -Number 2 -Path \\.\pipe\COM5 -Passthru # Used for Zwave

I have a ZigBee gateway [ConBee II] using Com4 on Hyper-V
I have an Aeotec Z-Stick Gen5 (ZW090) - UZB using Com5 on Hyper-V

I used ComPipe on the Hyper-V host to link Com4 and Com5 respectively.

.\COMpipe.exe -c \\.\COM4 -p \\.\pipe\COM4 # Used for Zigbee
.\COMpipe.exe -c \\.\COM5 -p \\.\pipe\COM5 # Used for Zwave

Set-VMComPort -Number has two options, 1 or 2.
1 sets the device to /dev/ttyS0
2 sets the device to /dev/ttyS1

S1 always works.
S0 gets communication errors and fails to connect to the dongle.

If I swap the COMPipe’s, S1 will work with the new dongle where S0 will fail with the new Dongle. This tells me HA can understand and communicate with whatever is on S1, whereas S0 always causes an issue.

Is there something in HA that would prevent ttyS0 from being used when mapped from the HyperVisor? If so, can it be moved?

S0 and S1 are the only options here.