Not an expert on DAQmx, this might be better question for DAQ. But here is what I know about that VI from the TSN prospective
The VI sets the same start time for all devices specified on the task wire. This could be either I/O time or host time. In this particular example the host is a cRIO-9040 which happens to be already synchronized with rest of the cDAQs specified on the task wire. The example will use the cRIO time in this case. But this example could very well have I/O time wired in and everything will work the same. This is because I/O time is also the same between the cRIO and all cDAQs (thanks to 802.1AS sync).
If you executed that code from a Windows host. Windows host time would be correlated(one time at start) to the 802.1AS time running on those devices and devices would start at that time. Then the TSN cDAQ devices will remain in sync within each other.
There are no DAQ PXI cards which can synchronize to 802.1AS or 1588 protocol. However, since the PXI card is used in a chassis with a PXI Linux controller, the PXI controller host time could be sync to 802.1AS via a PXI-6683 card. That is, the 6683 ethernet port could be connected to a 802.1AS or 1588 network, the 6683 would then sync the PXI controller host time to 802.1AS/1588 network time. Lastly, you could use host-time as the start source for your PXI DAQmx task. However, the only benefit you will get out of this configuration is the same start time. The I/O acquisition will not remain in sync since the PXI DAQ clock is not synchronized in any way with the network. I dont see any valid use case for such setup in real world, but maybe there is some :-).
In summary, a network of synchronized TSN devices (like in the example) will start at the same time and their IO will remain synchronized for the whole I/O acquisition. Thus resulting in a synchronized data from all devices within that network.
You could synchronize any NI Linux host time to 802.1AS/1588 in a way I described above but the only benefit you get from it is the same start time. The I/O from rest of the devices will not remain in sync.
I believe there is a way to synchronize multiple PXI chassis and DAQ cards together but that is not TSN(over network sync). I believe that is more of a signal synchronization where you literally wire clock out of one chassis to another. I have never done it, some PXI experts might be better source if you wish to take that route.
A common TSN setup is a PXI-6683 connected to a chain of cDAQ9185/9 or fDAQs, a TSN cRIO connected to a chain of cDAQ9185/9 or fDAQs, or simply a chain of of cDAQ9185/9 or fDAQs.
