OK so first things first: LXCFS is only responsible for displaying memory limits and usage, it doesn’t actually enforce any limits. This is what the kernel’s cgroups do (which are configured by LXD).
With regards to how swap is displayed inside the container please see https://github.com/lxc/lxcfs/blob/master/README.md#swap-handling, but it sounds like your host doesn’t have swap accounting on and is why you don’t see any swap usage.
Please note this doesn’t mean your containers aren’t using swap, it just means the kernel doesn’t provide the mechanism for LXCFS to display how much swap the container is using.
So the question is why are you seeing high load, and is the memory limit working?
Can you show output of cat /proc/meminfo on the host please?