Many DFO´s are hired for other purposes than making sense of flight operational manuals and has in many cases spend their recent years behind a desk doing less operational things - and some have forgotten what it means to be out in the real world on a daily basis. Probably the operators OM-B is just a piece of junk - written to satisfiy the authories... Say it isn´t so..
The OP, 172510, is clearly on the ball here with his question and challenging the operators (NCC I assume) manuals, with good reason. In a single pilot jet operation, flying into eg. Le Bourget etc. and you have the choice of using a speed (NOT V/S) control mode (such as FLCH) - that would be a wise choice from a flight safety perspective - any time the workload is high. With experience on type - he´ll find the thrust setting values and master this somewhat comfortably. Smart guy.