Yes I think this is spot on. From the RAIB report this driver had a history of doing it on NR as well, so there was certainly an element of ticking timebomb about it. I’d be interested to know exactly what training and instruction he would have received though, and the RAIB are surprisingly scant on that side of things.
You're right that the driver had a record of doing this, so I don't think the vast majority of Chiltern drivers would be doing the same but of course that's just a theoretical. I think the RAIB are scant because Chiltern's record keeping for training seems to be fairly poor and therefore they had no evidence either way.