If the railway's conditions are all at least as onerous as those applied by DVLA, then there's a logic in saying that if DVLA refuse to grant a licence, that excludes someone from driving. That's an entirely reasonable proxy measure, and still leaves room for occupational health assessments of those who don't drive a road vehicle.You’re probably right, but I’m not a medical professional, so couldn’t speculate with any degree of accuracy.
But the standards are different, often more restrictive, blood alcohol limits for an example off the top of my head.
I’m sure in the instances both you and I alluded to, it is more to do with the administrative/clerical/process of review from the DVLA.
But this isn’t an egalitarian policy, since owning a DVLA driving licence doesn’t preclude you from driving a train. So this medical standard doesn’t apply to all drivers, given that some may not possess a DVLA licence at all, so therefore it isn’t a fair ruling.
The issue, on which I suspect rail operator is no better than DVLA, is where DVLA's process for assessing evidence is fundamentally flawed, and doesn't respond in a timely way.