'Joker80's strength increases with time as expected, 
in the range from 0.4 sec to 36 sec per move, 
in a regular and theoretically expected way.'

'The effect you mention is observed NOT to occur
and thus cannot explain anything that was observed to occur.'

Admittedly, I have no proof ... yet.  Of course, this is due to Joker80
never have been playtested at truly long time controls (to my point of
view).
_______________________________________________________________

'Now if you want to conjecture that this will all miraculously become
very different at longer TC, you are welcome to test it and show us convincing results. I am not going to waste my computer time on such a wild and expensive goose chase.'

I respect your bravery to issue the challenge.  Although I would surely
find the results of a randomized Joker80 vs. non-randomized Joker80
tournament at 60 minutes per move (on average) interesting, I am not
willing either to invest a few (3-4) months of my computer time that I
estimate it would require to playtest 16 games under acceptable, reliable
conditions.

My refusal is due to it not being extremely important or worthwhile to me
just to keep the chess variant community from losing one potentially great
talent to numerology (or some such).  Besides, I have nothing to gain and
nothing new to learn by conducting this long, difficult experiment.  
Only you stand to benefit tangibly from its results.

I just cannot understand how any rational, intelligent man could believe
that introducing chaos (i.e., randomness) is beneficial (instead of
detrimental) to achieving a goal defined in terms of filtering-out
disorder to pinpoint order.  

When you reduce the power of your algorithm in any way to filter-out
inferior moves, you thereby reduce the average quality of the moves chosen
and consequently, you reduce the playing strength of your program- 
esp. at long time controls.  In other words, you are counteracting a
portion of everything desirable that you achieve thru advanced pruning
techniques used elsewhere within your program.

Since you argue that randomization is no problem at all and I argue
that randomization is a moderate-major problem, everything we say to 
one another is becoming purely argumentative.  Only tests (that neither 
one of us intend to perform) can prove who is correct and settle the
issue.
___________________________________________________________________

'As I explained, it is very easy to switch this feature off. 
But you should be prepared for significant loss of strength if you do
that.'

To the contrary, you should be prepared for a significant gain of strength
if you do that.  Notably, you do not dare.

In any event, the addition of the completely-unnecessary module of code 
used to create the randomization effect within Joker80 that you desire 
irrefutably makes your program larger, more complicated and slower.  
Can that be a good thing?