Found this that answers my question:
https://lists.xymon.com/archive/2015-April/041482.html
Will use timeout to mitigate.
From: Max Xu <user-0e2fe6810b65@xymon.invalid>
Date: Friday, June 5, 2020 at 12:17 PM
To: "xymon at xymon.com" <xymon at xymon.com>
Subject: why nfs mounts are excluded from xymon analysis
HI,
I see xymon analysis.cfg DISK settings not covering nfs mounts because they are excluded from [df].
We have use cases to cover disk usage on nfs mounts. If I change xymonclient-linux.sh to un-exclude nfs and nfs4, is there any potential side effects given I don?t know the reasons why they are currently being excluded.
Thanks,
-Max