It's nice to hear that you are looking into all this - if you look at Ulf's minutes of the Berlin BoF session, I have an action item to test OF's IDDES in the channel!
First up, I can't find the picture that you refer to...?
Nonetheless I have some comments that might be helpful:
Re=395 and such high resolution should result in a fully-resolved LES, and is hence not the most ideal test of IDDES running as a wall-modelled LES (WMLES). I'd agree that IDDES should, in the limit of a fully-resolved LES reduce to pure LES mode and should give good results, however that would first be worth testing once you've validated the implementation with a WMLES case.
I would also recommend switching off the hybrid scheme and running with pure CDS ("linear") - for this case, the grid is fine enough everywhere for full CDS and channel flow is extremely sensitive to just a little bit of dissipation. As above, a later test case with the hybrid scheme would be an interesting idea, but pure CDS gives you the least setup uncertainty to start with.
It was all a long time ago, but I think I remember that we found problems both with IDDES for fully-resolved LES (low-Re) and for channel flow in combination with the hybrid scheme... all in the direction of an excessively "high" log law.
For a basic verificaton I'd suggest the following case, for which I could provide ASCII data of various blending functions, eddy viscosity, velocity profiles etc. from our in-house code and (I'll ask them for permission first) the results of Shur et al. An example plot is attached.
Re_tau = 18000
(fix pressure gradient dp/dx = -1 and set rho = 1 and viscosity = 1/18000)
Domain size L_x = 6.4 \delta, L_y = 2 \delta, L_z = 3.2 \delta.
Tangential grid resolution: Delta_x = 0.1, Delta_z = 0.05. (i.e. 64 cells in the x and z directions).
Wall-normal grid with y^+ of first cell vertex
= 1., stretching ratio around 1.12.
"linear" convection scheme
Would you be interested in running such a simulation for a direct code-to-code verification? If I forgot any details or if you have any questions don't hesitate to ask.