Normally i would have called this indexing the plark plug, but it doesnt normally entail the plug to be lifted out of the chamber.
The idea of indexing is to direct the spark towards the inlet of air/fuel this can create a better fire in the chamber.
If plugs arent indexed the electrode can theoretic sheild the spark as a worst case senario.
Having the plugs out of the chamber can in terms reduce the compression ratio. I use to machine done the washers on 50cc 2stroke pocket bike engines to get a little more compression
Cheers
Jake