Hello Pritesh,
No inconvenience at all! The documents on the link that you shared are from Fluent 12 (2009). I see that from Fluent 18, the option was removed, but the reason is not explicitely documented in any of the release notes.
To add to this, I must say that we typically support the current release, today 23R1, and the two previous releases, today 22R2, 22R1.
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