Yes, fictitious clearance is like an artificial clearance. I used it to compress the bearings in order to make it look more realistic and also to attain stability. 
Solver necessarily doesn’t need this. I first ran the simulation without clearance and it also worked, took more time but the results were not quite good due to coarse mesh and little gap between the contact surfaces (specially outer ring one).
It is not about geometrical gap since I need to compress it rather then creating a gap. So in other words, if you even have a gap between two contacting surfaces, then rather then modifying your geometry you can use fictitious clearance to artificially remove the gap 
My pleasure! stay tuned for the final results 
Best,
Ahmed