What I would say about this is that the wearing of chest protectors in the sort of training that is described in this thread is becoming increasingly common. The question of whether you must train in the same gear as you play in is a different question. I think that's a matter of personal preference/obsession.
The other trend that we are seeing is the increasing use of chest protectors by bowlers who don't want to risk a rib injury. When Mickey Arthur was coach of South Africa he used to insist on all his fast bowlers wearing Aero chest protectors because the downside to the team of an injury far exceeded the slight inconvenience of having to wear one (especially one of our ones
).