Yes, the original poster did indeed ask this advice and counsel...which you incorrectly provided based on ancient information. This is no longer 1966, as you may not be aware.
It makes no difference.
The information is as valid today on the referenced aircraft as it was when it was manufactured.
STC's notwithstanding...which were not asked about nor referenced in the original question.
Is there a benefit in having the ice vanes open during a normal takeoff/landing on a gravel strip or on a sealed runway in temperatures above freezing?
My advice and councel, as stated previously...
On a gravel strip? Yes.
On a sealed runway in temperatures above freezing?
None whatsoever, and will present an unnecessary takeoff performance penalty, if used.