EQ Boost cars question

[Dewi 2]

The starter/generator EQ Boost system, is now fitted to many recent Mercedes models.
A 48 volt electric motor, fitted between engine and transmission, replaces the starter motor and alternator, also boosts turbo-lag and maybe does other things.

The function to 'fill-in' for turbo lag is by supplying up to 20 bhp boost when accelerating at lower revs.
I had thought the motor applied the boost power directly to the crankshaft.
However, a motoring review that I read recently, stated it is the turbocharger is spun electrically when boost is needed.

Therefore confused now, so can anyone explain the true way in which EQ Boost operates ?